Superconductivity in Mg₂IR₃Si: A fully ordered laves phase

Novel ternary Laves phase compounds were explored, and Mg₂Ir₃Si was synthesized via a solid-state reaction. X-ray diffraction studies revealed that Mg₂Ir₃Si crystallizes in a Mg₂Cu₃Si-type structure (P6₃=mmc, D_6h ⁴, No. 194), which corresponds to a fully ordered variant of hexagonal Laves phase MgZn₂. The structure is composed of a hexagonal diamond network of Mg atoms, a breathing Kagome network of Ir atoms, and a triangular network of Si atoms. Electrical resistivity, magnetization, and specific heat measurements of Mg₂Ir₃Si revealed that it exhibits superconductivity with a transition temperature of 7 K. This compound is compared to another Laves phase compound, Li₂IrSi₃, in which the positions of Ir and Si are interchanged; Li₂IrSi₃ has a superconducting transition temperature of 3.8 K. The results obtained demonstrate that both Ir and Si Kagome networks can occur in fully ordered Laves phase compounds, i.e., in Mg₂Ir₃Si and Li₂IrSi₃, and the former is preferable for superconductivity.