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Stürzer, Tobias; Stürzer, Christine; Johrendt, Dirk (2017): Iron arsenide superconductors (CaFeAs)(10)MnAs8 with metallic interlayers (M=Pt, Pd;n=3, 4). In: Physica Status Solidi B-Basic Solid State Physics, Vol. 254, No. 1, 1600417
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The compounds referred to as 1038 and 1048 phases (CaFeAs)(10)PtnAs8 (n=3,4) are the structurally most complex iron arsenide superconductors and the first examples with metallic interlayers. The electronic subsystems of FeAs and PtnAs8 layers hardly interact and the contribution of the metallic PtnAs8 interlayers to the Fermi surface is so small that the typical nesting is not degraded. (CaFeAs)(10)Pt3As8 is the parent compound of the 1038/1048 materials which undergoes the typical magneto-structural phase transition in spite of the already triclinic lattice. Superconductivity is controlled by the same doping mechanisms as known from simpler FeAs systems. High critical temperatures up to 38K occur in both 1038 and 1048 phases if the FeAs layers are clean (free from Pt) and electron doped by charge transfer either from Pt4As8 in 1048 or by rare-earth doping of the calcium layer in 1038 compounds. The presence of two negatively charged layers (FeAs)(-) and (PtnAs8)(-) which compete for the electrons transferred from the Ca2+ ions is unique in the family of iron arsenide superconductors. Geometric incompatibilities of the FeAs and PtnAs8 slabs cause severe stacking disorder. The robustness of superconductivity against low lattice symmetry and significant structural imperfection of the interlayer is quite remarkable and underlines that the FeAs slabs are the key in controlling and understanding high-temperature superconductivity in iron arsenides. [GRAPICS] Crystal structure of (CaFeAs)(10)Pt3As8 and the Pt3As8 layer. (C) 2016 Wiley-Blackwell-VCH Verlag GmbH & Co. KGaA, Weinheim