Superconductivity in Hexagonal BaPtAs: SrPtSb-and YPtAs-Type Structures with Ordered Honeycomb Network

The crystal structure and superconductivity of hexagonal BaPtAs are reported. Single-crystal X-ray diffraction, magnetization, electrical resistivity, and specific heat measurements were performed in this study. Two hexagonal structures with different PtAs honeycomb network stacking sequences, namely, SrPtSb-(space group P6m2, D13 h, No. 187) and YPtAs-Type (P63/mmc, D46 h, No. 194) structures, were identified and found to exhibit superconductivity at 2.8 and 2.1' 3.0 K, respectively. In contrast, the cubic LaIrSi-Type structure (P213, T4, No. 198) did not exhibit superconductivity above 0.1 K. BaPtAs provides a unique opportunity to study superconductivity with broken and preserved spatial inversion symmetry.