The structures of the equiatomic germanides REPdGe with the heavy rare earth elements have been reinvestigated with respect to palladium-germanium ordering. The samples were prepared by arc-melting of the elements followed by annealing procedures in sealed silica ampoules at different temperatures. The structures of YPdGe, HT-TbPdGe, LT-DyPdGe, HT-DyPdGe, LT-HoPdGe, HT-HoPdGe, ErPdGe, and TmPdGe, and of the new germanide LuPdGe, were refined from single crystal diffractometer data. LT-DyPdGe and LT-HoPdGe crystallize with the YPdSi-type structure, space group Pmmn. The other germanides crystallize with the non-centrosymmetric YbAuSn structure, space group Imm2. All structures are orthorhombically-distorted superstructure variants of AlB2, and they show strong intralayer Pd-Ge bonding within the ordered Pd3Ge3 hexagons. There is weak Pd-Ge and Pd-Pd interlayer bonding. The crystal chemical relationship between the different superstructures is discussed.
Graphical Abstract
Polymorphism in the Germanides REPdGe with the Heavy Rare Earth Elements
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