The new double perovskite Mn2MnReO6 has been synthesised at high pressure. Mn(2+) and Re(6+) spins order antiferromagnetically through two successive transitions that are coupled by magnetoelastic effects, as order of the Mn spins at 109 K leads to lattice distortions that reduce frustration prompting Re order at 99 K.

EuPtAl has been prepared from the elements via arc-melting and subsequent temperature treatment; the structure was refined from single crystal X-ray diffraction data. The compound crystallizes in an orthorhombic (3 + 1)D commensurately modulated structure (ScPtAl type) with space group Cmcm(α,0,0)0 s0 (α = 2/3). Full ordering of the Pt and Al atoms within the [PtAl] polyanion was observed. Magnetic measurements revealed an anomaly in the susceptibility data at T = 41.6(1) K, which was also observed as λ-type anomaly in heat capacity measurements ( T = 40.7(1) K). Temperature dependent powder X-ray diffraction experiments indicated a drastic shortening of the c axis (-18 pm, -1.1%) around 45 K, while the a axis nearly remains the same (-1 pm, -0.2%). Measurements of the electrical resistivity verified the anomaly, indicating a clear change in the electronic structure of the material. The observed anomalies in the physical measurements can be explained by a temperature driven first order valence change from Eu at higher temperatures (>55 K) to Eu at low temperatures. This valence change was proven by temperature dependent Eu Mössbauer spectroscopic investigations. Isostructural EuPtGa was prepared in comparison, and it shows divalent Eu atoms down to 2.5 K along with antiferromagnetic ordering at T = 13.1(1) K.

Ba3Pt4Al4 was prepared from the elements in niobium ampules and crystallizes in an orthorhombic structure, space group Cmcm (oP44, a = 1073.07(3), b = 812.30(3), c = 1182.69(3) pm) isopointal to the Zintl phase A2Zn5As4 (A = K, Rb). The structure features strands of distorted [Pt4Al4] heterocubane-like units connected by condensation over Pt/Al edges. These are arranged in a hexagonal rod packing by further condensation over Pt and Al atoms with the barium atoms located inside cavities of the [Pt4Al4](δ-) framework. Structural relaxation confirmed the electronic stability of the new phase, while band structure calculations indicate metallic behavior. Crystal orbital Hamilton bonding analysis coupled with Bader effective charge analysis suggest a polar intermetallic phase in which strong Al-Pt covalent bonds are present, while a significant electron transfer from Ba to the [Pt4Al4](δ-) network is found. By X-ray photoelectron spectroscopy measurements the Pt 4f5/2 and 4f7/2 energies for Ba3Pt4Al4 were found in the range of those of elemental Pt due to the electron transfer of Ba, while PtAl and PtAl2 show a pronounced shift toward a more cationic platinum state. (27)Al magic-angle spinning NMR investigations verified the two independent crystallographic Al sites with differently distorted tetrahedrally coordinated [AlPt4] units. Peak assignments could be made based on both geometrical considerations and in relation to electric field gradient calculations.

Structural and property investigations of the five Zintl phases Eu5In2Pn6 and Eu3MAs3 (Pn = As–Bi; M = Al, Ga) including magnetic and 121Sb and 151Eu Mössbauer spectroscopic measurements.

REPd5Al2 compounds with RE = Ce–Gd as well as Y and Lu have been previously synthesized. Although some compounds with the small lanthanides also exist, the compounds with intermediate-sized rare-earth elements (RE = Tb–Yb) had not been prepared. We report on the missing members of the REPd5Al2 (RE = Tb–Yb) series as well as on the new REPt5Al2 (RE = Y, Gd–Tm, Lu) series, which we have synthesized and structurally as well as magnetically characterized. All members crystallize isostructurally in the ZrNi2Al5 type with an anti-arrangement of the T = Pd/Pt and Al atoms. YPd5Al2 and LuPd5Al2, as well as the respective platinum homologs, YPt5Al2 and LuPt5Al2, have been characterized also by 27Al magic-angle spinning nuclear magnetic resonance spectroscopy. Consistent with the XRD analysis, the spectra indicate the existence of only one distinct Al site in the structure.

The five ternary intermetallic compounds

Four new MPtAl2 (M=Ca, Sr, Ba, Eu) compounds, adopting the orthorhombic MgCuAl2‐type structure, have been synthesized from the elements using tantalum ampoules. All compounds are obtained as platelet‐shaped crystallites and exhibit an increasing moisture sensitivity with increasing size of the formal M cation. Structural investigations indicate a pronounced elongation of the crystallographic b‐axis, which results in a significant distortion of the [PtAl2]δ− polyanion. Within the polyanion, layer‐like arrangements can be found with bonding Pt−Al interactions within the slab; the increase of the b‐axis can be attributed to increasing Al−Al distances and therefore decreasing interactions between the slabs, caused by the differently‐sized formal M cations. While the alkaline earth (M=Ca, Sr) representatives exhibit Pauli paramagnetism, BaPtAl2 shows diamagnetic behavior, finally EuPtAl2 is ferromagnetic with TC=54.0(5) K. The effective magnetic moment indicates that the Eu atoms are in a divalent oxidation state, which is confirmed by 151Eu Mössbauer spectroscopic investigations. Measurements below the Curie‐temperature show a full magnetic hyperfine field splitting with Bhf=21.7(1) T. 27Al and 195Pt magic‐angle spinning NMR spectroscopy corroborates the presence of single crystallographic sites for the Pt and Al atoms. The large 27Al nuclear electric quadrupolar coupling constants confirm unusually strong electric field gradients, in agreement with the structural distortions and the respective theoretical calculations. X‐ray photoelectron spectroscopy has been utilized to investigate the charge transfer within the polyanion. The Pt 4f binding energy decreases with decreasing electronegativity / ionization energy of the alkaline earth elements, suggesting an increasing electron density at the Pt atoms. Theoretical investigations underline the platinide character of the investigated compounds by Bader charge calculations. The analysis of the integrated crystal orbital Hamilton population (ICOHP) values, electron localization function (ELF) and isosurface analyses lead to a consistent structural picture, indicating stable layer‐like arrangements of the [PtAl2]δ− polyanion.

A temperature induced valence phase transition from Yb3+ at higher temperatures to Yb2+ at lower temperatures was observed at T = 110(1) K for intermetallic YbPd2Al3.