Preparation, Crystal Structure and Physical Properties of the Superconducting Cage Compound Ba 3 Ge 16 Ir 4

The cage compound Ba 3 Ge 16 Ir 4 crystallizes with the Ba 3 Ge 16 Rh 4 type of crystal structure, which represents a hierarchical derivative of the BaAl 4 type. The crystal structure [Pearson symbol tI 46, space group I 4/ mmm ; a = 6.5312(2) Å, c = 22.2845(6) Å] was refined from single‐crystal X‐ray diffraction data. The phase was obtained after 10 d at 910 °C with small impurities of clathrate‐I, BaGe 7 Ir 2 and α‐Ge remaining at the grain boundaries. Ba 3 Ge 16 Ir 4 is a Pauli‐paramagnetic metal, which becomes superconducting below T c = 5.1 K. Electronic structure and analysis of the chemical bonding were performed based on density functional theory calculations. The physical properties are discussed in comparison to the isotypic phase Ba 3 Ge 16 Rh 4 .