  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 $P\bar{6}m2$, $D_{3h}^1$, No. 187) and YPtAs-type
($P6_3/mmc$, $D_{6h}^4$, 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 ($P2_13$, $T^4$, 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.
