ScAl3C3 crystallizes in the hexagonal P6_3mc space group. Sc(1) is bonded to three equivalent C(2) and three equivalent C(3) atoms to form ScC6 octahedra that share corners with three equivalent Al(1)C4 tetrahedra, corners with three equivalent Al(2)C4 tetrahedra, edges with six equivalent Sc(1)C6 octahedra, edges with three equivalent Al(1)C4 tetrahedra, and edges with three equivalent Al(2)C4 tetrahedra. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded to one C(1) and three equivalent C(2) atoms to form AlC4 tetrahedra that share corners with three equivalent Sc(1)C6 octahedra,  a cornercorner with one Al(2)C4 tetrahedra, corners with six equivalent Al(1)C4 tetrahedra, and edges with three equivalent Sc(1)C6 octahedra. The corner-sharing octahedral tilt angles are 20°. In the second Al site, Al(2) is bonded to one C(1) and three equivalent C(3) atoms to form AlC4 tetrahedra that share corners with three equivalent Sc(1)C6 octahedra,  a cornercorner with one Al(1)C4 tetrahedra, corners with six equivalent Al(2)C4 tetrahedra, and edges with three equivalent Sc(1)C6 octahedra. The corner-sharing octahedral tilt angles are 14°. In the third Al site, Al(3) is bonded in a distorted trigonal planar geometry to one C(2) and three equivalent C(1) atoms. There are three inequivalent C sites. In the first C site, C(1) is bonded to one Al(1), one Al(2), and three equivalent Al(3) atoms to form CAl5 trigonal bipyramids that share corners with three equivalent C(3)Sc3Al3 octahedra and corners with six equivalent C(1)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 68°. In the second C site, C(2) is bonded in a 7-coordinate geometry to three equivalent Sc(1), one Al(3), and three equivalent Al(1) atoms. In the third C site, C(3) is bonded to three equivalent Sc(1) and three equivalent Al(2) atoms to form CSc3Al3 octahedra that share corners with three equivalent C(1)Al5 trigonal bipyramids and edges with six equivalent C(3)Sc3Al3 octahedra.
ScAl3C3 crystallizes in the hexagonal P6_3mc space group. Sc(1) is bonded to three equivalent C(2) and three equivalent C(3) atoms to form ScC6 octahedra that share corners with three equivalent Al(1)C4 tetrahedra, corners with three equivalent Al(2)C4 tetrahedra, edges with six equivalent Sc(1)C6 octahedra, edges with three equivalent Al(1)C4 tetrahedra, and edges with three equivalent Al(2)C4 tetrahedra. All Sc(1)-C(2) bond lengths are 2.47 Å. All Sc(1)-C(3) bond lengths are 2.39 Å. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded to one C(1) and three equivalent C(2) atoms to form AlC4 tetrahedra that share corners with three equivalent Sc(1)C6 octahedra,  a cornercorner with one Al(2)C4 tetrahedra, corners with six equivalent Al(1)C4 tetrahedra, and edges with three equivalent Sc(1)C6 octahedra. The corner-sharing octahedral tilt angles are 20°. The Al(1)-C(1) bond length is 2.04 Å. All Al(1)-C(2) bond lengths are 2.05 Å. In the second Al site, Al(2) is bonded to one C(1) and three equivalent C(3) atoms to form AlC4 tetrahedra that share corners with three equivalent Sc(1)C6 octahedra,  a cornercorner with one Al(1)C4 tetrahedra, corners with six equivalent Al(2)C4 tetrahedra, and edges with three equivalent Sc(1)C6 octahedra. The corner-sharing octahedral tilt angles are 14°. The Al(2)-C(1) bond length is 2.02 Å. All Al(2)-C(3) bond lengths are 2.09 Å. In the third Al site, Al(3) is bonded in a distorted trigonal planar geometry to one C(2) and three equivalent C(1) atoms. The Al(3)-C(2) bond length is 2.58 Å. All Al(3)-C(1) bond lengths are 1.95 Å. There are three inequivalent C sites. In the first C site, C(1) is bonded to one Al(1), one Al(2), and three equivalent Al(3) atoms to form CAl5 trigonal bipyramids that share corners with three equivalent C(3)Sc3Al3 octahedra and corners with six equivalent C(1)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 68°. In the second C site, C(2) is bonded in a 7-coordinate geometry to three equivalent Sc(1), one Al(3), and three equivalent Al(1) atoms. In the third C site, C(3) is bonded to three equivalent Sc(1) and three equivalent Al(2) atoms to form CSc3Al3 octahedra that share corners with three equivalent C(1)Al5 trigonal bipyramids and edges with six equivalent C(3)Sc3Al3 octahedra.