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 P6m2P, D3h1, No. 187) and YPtAs-type (P63/mmc, D6h4, 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.