Ta4AlC3 is MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded in a 3-coordinate geometry to three equivalent Al(1) and three equivalent C(1) atoms. In the second Ta site, Ta(2) is bonded to three equivalent C(1) and three equivalent C(2) atoms to form a mixture of distorted edge and corner-sharing TaC6 pentagonal pyramids. Al(1) is bonded in a 6-coordinate geometry to six equivalent Ta(1) atoms. There are two inequivalent C sites. In the first C site, C(1) is bonded to three equivalent Ta(1) and three equivalent Ta(2) atoms to form a mixture of edge, corner, and face-sharing CTa6 octahedra. The corner-sharing octahedral tilt angles are 47°. In the second C site, C(2) is bonded to six equivalent Ta(2) atoms to form a mixture of edge, corner, and face-sharing CTa6 octahedra. The corner-sharing octahedral tilt angles are 47°.
Ta4AlC3 is MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded in a 3-coordinate geometry to three equivalent Al(1) and three equivalent C(1) atoms. All Ta(1)-Al(1) bond lengths are 2.87 Å. All Ta(1)-C(1) bond lengths are 2.16 Å. In the second Ta site, Ta(2) is bonded to three equivalent C(1) and three equivalent C(2) atoms to form a mixture of distorted edge and corner-sharing TaC6 pentagonal pyramids. All Ta(2)-C(1) bond lengths are 2.26 Å. All Ta(2)-C(2) bond lengths are 2.24 Å. Al(1) is bonded in a 6-coordinate geometry to six equivalent Ta(1) atoms. There are two inequivalent C sites. In the first C site, C(1) is bonded to three equivalent Ta(1) and three equivalent Ta(2) atoms to form a mixture of edge, corner, and face-sharing CTa6 octahedra. The corner-sharing octahedral tilt angles are 47°. In the second C site, C(2) is bonded to six equivalent Ta(2) atoms to form a mixture of edge, corner, and face-sharing CTa6 octahedra. The corner-sharing octahedral tilt angles are 47°.