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Two new compounds with the LaOAgS structure, EuFZnAs (1) and EuFZnSb (2), were obtained via solid state reaction. Both compounds are tetragonal (P4/nmm) with the cell parameters a = 4.1000(1) Å and c = 9.0811(1) Å for 1 and a = 4.2852(1)Å and c = 9.4238(1)Å for 2. The absence of their phosphide analog can be explained based on crystal chemical considerations as well as on quantum-chemical estimates of their thermodynamic stability with respect to EuF and EuZnPn. The magnetic response of 1 and 2 is ascribed to the presence of Eu ions. Both compounds are paramagnetic down to low temperatures, where they order antiferromagnetically at ∼5 K and ∼3 K, respectively. They are narrow-gap semiconductors, and EuFZnSb demonstrates a relatively high value of the Seebeck coefficient.

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Two new ternary arsenides, namely, Eu7Cu44As23 and Sr7Cu44As23, were synthesized from elements at 800 °C. Their crystal structure represents a new filled version of the BaHg11 motif with cubic voids alternately occupied by Eu(Sr) and As atoms, resulting in a 2 × 2 × 2 superstructure of the aristotype: space group Fm3̅m, a = 16.6707(2) Å and 16.7467(2) Å, respectively. The Eu derivative exhibits ferromagnetic ordering below 17.5 K. In agreement with band structure calculations both compounds are metals, exhibiting relatively low thermopower, but high electrical and low thermal conductivity.

This relatively low-temperature process involves complete rearrangement of the crystal structure-from a 2D architecture featuring slabs [Pb 2 F 2 ] 2+ formed by fluorine-centered tetrahedra into a structure characterized by 1D motifs based on [OPb 2 ] 2+ chains of oxocentered tetrahedra. The comparative crystal chemistry of the obtained anion-centered structural architectures is discussed. (Siidra et al. 2013c(Siidra et al. , 2015. Most of these structures can be notionally decomposed into tetragonal subcells with an a parameter similar to that of litharge (commonly 3.75-4.35 Å, depending on the layer composition), while c can vary over a wide range (from 5 to more than 75 Å) as might be expected for layered structures (Charkin 2008). Within these "archetypic" subcells, the 2 ∞ [XM] (X = anion, M = cation) slabs contain two X and two M atoms; they are positively charged and interleave with various anionic species. The OM 4 oxocentered tetrahedra, with M = Pb 2+ , Bi 3+ or rare-earth elements, are the most common contributors to these slabs. Second rank the FM 4 fluoride-centered tetrahedra with M being rare-earth or alkaline-earth elements, but most commonly Pb 2+ . [Pb 2 F 2 ] 2+ slabs have been found in the structures of the minerals matlockite [Pb 2 F 2 ](Cl) 2 (c = 9 Å) (Pasero and Perchiazzi 1996), grandreefite [Pb 2 F 2 ](SO 4 ) (c = 14 Å)

The first magnetic unconventional clathrate EuNi2P4 has been prepared and its thermodynamic properties have been investigated.

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Heat capacity C P (T) (2-300 K) and unit cell parameters a(T), b(T), and c(T) (5-300 K) of type-VII clathrates SrNi 2 P 4 and BaNi 2 P 4 have been investigated experimentally. The studied compounds are prepared by a two-stage ampoule synthesis. Diffuse maxima of C P (T) near 5 K along with anomalies in temperature dependencies of unit cell parameters below 10 K are observed and related to the influence of two-level systems in guest-atom substructures. Joint analysis of temperature dependencies of heat capacity and unit cell volume of both clathrates within the frames of the Debye-Einstein model allowed determining characteristic temperatures of the clathrate frameworks and guest atoms as well as parameters of the two-level systems. The relationships of the obtained characteristics and the peculiarities of the crystal structures of SrNi 2 P 4 and BaNi 2 P 4 are discussed.