Superconductivity of the partially ordered laves phase Mg₂Ir_2.3Ge_1.7

A novel ternary Laves phase Mg₂Ir_2.3Ge_1.7 was synthesized in this study. Single-crystal X-ray diffraction experiments confirmed a Mg₂Cu₃Si-type structure (P6₃=mmc, D⁴₆h, No. 194). The structure comprises a Mg hexagonal diamond, an Ir=Ge breathing Kagome network, and a Ge triangular networks; it is thus classified as a partially ordered Laves phase that is neither ordered nor disordered. This is in contrast to the isoelectronic Mg₂Ir₃Si with a fully ordered Laves phase structure. Magnetization and resistivity measurements show that bulk superconductivity occurs at 5.3 K in Mg₂Ir_2.3Ge_1.7. The partially ordered phase is important because it forms a link between the disordered and ordered Laves phases. Moreover, our findings would provide an opportunity to study the effects of disorder on the breathing Kagome network.