Superconducting [(Li1−xFex)OH](Fe1−yLiy)Se (x≈0.2, y≈0.08) was synthesized by hydrothermal methods and characterized by single‐crystal and powder X‐ray diffraction. The structure contains alternating layers of anti‐PbO type (Fe1−yLiy)Se and (Li1−xFex)OH. Electrical resistivity and magnetic susceptibility measurements reveal superconductivity at 43 K. An anomaly in the diamagnetic shielding indicates ferromagnetic ordering near 10 K while superconductivity is retained. The ferromagnetism is from the iron atoms in the (Li1−xFex)OH layer. Isothermal magnetization measurements confirm the superposition of ferromagnetic and superconducting hysteresis. The internal ferromagnetic field is larger than the lower, but smaller than the upper critical field of the superconductor. The formation of a spontaneous vortex phase where both orders coexist is supported by 57Fe‐Mössbauer spectra, 7Li‐NMR spectra, and μSR experiments.

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A new crystal growth technique for single-crystals of RE FeAsO (RE = La, Ce, Pr, Nd, Sm, Gd, and Tb) using NaI/KI as flux is presented. Crystals with a size up to 300 µm were isolated for single-crystal X-ray diffraction measurements. Lattice parameters were determined by LeBail fits of X-ray powder data against LaB6 standard. A consistent set of structural data is obtained and interpreted in a hard-sphere model. Effective radii for the rare-earth metal atoms for RE FeAsO are deduced. The relation of the intra-and inter-plane distances of the arsenic atoms is identified as limiter of the phase formation, and its influence on Tc is discussed.

Room-temperature precipitation from aqueous solutions yields the hitherto unknown metastable stoichiometric iron selenide (ms-FeSe) with tetragonal anti-PbO type structure. Samples with improved crystallinity are obtained by diffusion-controlled precipitation or hydrothermal recrystallization. The relations of ms-FeSe to superconducting β-FeSe(1-x) and other neighbor phases of the iron-selenium system are established by high-temperature X-ray diffraction, DSC/TG/MS (differential scanning calorimetry/thermogravimetry/mass spectroscopy), (57)Fe Mössbauer spectroscopy, magnetization measurements, and transmission electron microscopy. Above 300 °C, ms-FeSe decomposes irreversibly to β-FeSe(1-x) and Fe(7)Se(8). The structural parameters of ms-FeSe (P4/nmm, a = 377.90(1) pm, c = 551.11(3) pm, Z = 2), obtained by Rietveld refinement, differ significantly from literature data for β-FeSe(1-x). The Mössbauer spectrum rules out interstitial iron atoms or additional phases. Magnetization data suggest canted antiferromagnetism below T(N) = 50 K. Stoichiometric non-superconducting ms-FeSe can be regarded as the true "parent" compound for the "11" iron-chalcogenide superconductors and may serve as starting point for new chemical modifications.

New monoclinic polymorphs of RE 2 FeSe 2 O 2 (RE = La, Ce) were synthesized at 800°C in a NaI/KI flux, and characterized by single-crystal X-ray diffraction (C2/m, Z = 2). mC-La 2 FeSe 2 O 2 and mC-Ce 2 FeSe 2 O 2 represent new structures in the RE 2 FeSe 2 O 2 family, and contain iron atoms exclusively in a distorted octahedral coordination of four selenium and two oxygen atoms. Such FeSe 4 O 2 octahedra occur together with FeSe 4 -tetrahedra if the synthesis temperature in-

Coexistence of 3d-Ferromagnetism and Superconductivity in [(Li 1-xFex)OH](Fe1-yLiy)Se. -(Li0.795Fe0.205)OH(Fe0.915Li0.085)Se is hydrothermally prepared from a mixture of iron metal, selenourea, and LiOH in H 2O (autoclave, 150 C, 8 d) and characterized by powder and single crystal XRD, SEM, 57 Fe-Moessbauer spectroscopy, and DFT electronic structure calculations. Electrical resistivity and magnetic susceptibility measurements reveal superconductivity at 43 K, and ferromagnetic ordering near 10 K while superconductivity is retained. The compound crystallizes in the tetragonal space group P4/nmm with Z = 2. The structure contains superconducting (Fe 1-yLiy)Se layers and ferromagnetic (Li1-xFex)OH (x  0.2, y  0.08) layers, which alternate and show anti-PbO type structures. -(PACHMAYR, U.; NITSCHE, F.; LUETKENS, H.; KAMUSELLA, S.; BRUECKNER, F.; SARKAR, R.; KLAUSS, H.-H.; JOHRENDT*, D.; Angew. Chem., Int. Ed. 54 (2015) 1, 293-297, http://dx.

The selenide oxides REMn 0.5 SeO (RE = La, Ce) were synthesized by heating RE 2 O 3 , RE, Mn, and Se in a NaI/KI flux at 800°C, and their modulated crystal structures determined by X-ray single crystal and powder diffraction {P 1 1 2/n(αβ½)0s, Z = 2, LaMn 0.5 SeO: a = 405.7(1), b = 405.7(1), c = 915.2(1) pm, γ = 90°, q = [1/10, -1/10, ½]; CeMn 0.5 SeO: a = 402.0(1), b = 401.8(1), c = 910.7(1) pm, γ = 90.000(4)°, q = [0.0789(2), -0.0783 (2), ½]}. The structures are related to the ZrCuSiAs-type structure with ordered vacancies at the manga-

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