Al4SiC4 is Aluminum carbonitride-like structured and crystallizes in the hexagonal P6_3mc space group. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one C(1) and three equivalent C(2) atoms to form distorted AlC4 tetrahedra that share  a cornercorner with one Si(1)C4 tetrahedra, corners with three equivalent Al(3)C4 tetrahedra, corners with six equivalent Al(1)C4 tetrahedra, and edges with three equivalent Al(2)C4 trigonal pyramids. In the second Al site, Al(2) is bonded to one C(2) and three equivalent C(1) atoms to form distorted AlC4 trigonal pyramids that share  a cornercorner with one Al(3)C4 tetrahedra, corners with three equivalent Si(1)C4 tetrahedra, corners with six equivalent Al(2)C4 trigonal pyramids, and edges with three equivalent Al(1)C4 tetrahedra. In the third Al site, Al(3) is bonded to one C(2) and three equivalent C(4) atoms to form a mixture of distorted edge and corner-sharing AlC4 tetrahedra. In the fourth Al site, Al(4) is bonded to one C(3) and three equivalent C(4) atoms to form AlC4 tetrahedra that share corners with three equivalent Al(3)C4 tetrahedra, corners with three equivalent Si(1)C4 tetrahedra, corners with six equivalent Al(4)C4 tetrahedra, and edges with three equivalent Al(3)C4 tetrahedra. Si(1) is bonded to one C(1) and three equivalent C(3) atoms to form SiC4 tetrahedra that share  a cornercorner with one Al(1)C4 tetrahedra, corners with three equivalent Al(4)C4 tetrahedra, corners with six equivalent Si(1)C4 tetrahedra, and corners with three equivalent Al(2)C4 trigonal pyramids. There are four inequivalent C sites. In the first C site, C(1) is bonded to one Al(1), three equivalent Al(2), and one Si(1) atom to form CAl4Si trigonal bipyramids that share corners with three equivalent C(3)AlSi3 tetrahedra, corners with six equivalent C(1)Al4Si trigonal bipyramids, and edges with three equivalent C(2)Al5 trigonal bipyramids. In the second C site, C(2) is bonded to one Al(2), one Al(3), and three equivalent Al(1) atoms to form distorted CAl5 trigonal bipyramids that share corners with three equivalent C(4)Al6 octahedra, corners with six equivalent C(2)Al5 trigonal bipyramids, and edges with three equivalent C(1)Al4Si trigonal bipyramids. The corner-sharing octahedral tilt angles are 62°. In the third C site, C(3) is bonded to one Al(4) and three equivalent Si(1) atoms to form CAlSi3 tetrahedra that share corners with three equivalent C(4)Al6 octahedra, corners with six equivalent C(3)AlSi3 tetrahedra, and corners with three equivalent C(1)Al4Si trigonal bipyramids. The corner-sharing octahedral tilt angles are 62°. In the fourth C site, C(4) is bonded to three equivalent Al(3) and three equivalent Al(4) atoms to form CAl6 octahedra that share corners with three equivalent C(3)AlSi3 tetrahedra, corners with three equivalent C(2)Al5 trigonal bipyramids, and edges with six equivalent C(4)Al6 octahedra.
Al4SiC4 is Aluminum carbonitride-like structured and crystallizes in the hexagonal P6_3mc space group. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one C(1) and three equivalent C(2) atoms to form distorted AlC4 tetrahedra that share  a cornercorner with one Si(1)C4 tetrahedra, corners with three equivalent Al(3)C4 tetrahedra, corners with six equivalent Al(1)C4 tetrahedra, and edges with three equivalent Al(2)C4 trigonal pyramids. The Al(1)-C(1) bond length is 2.19 Å. All Al(1)-C(2) bond lengths are 1.93 Å. In the second Al site, Al(2) is bonded to one C(2) and three equivalent C(1) atoms to form distorted AlC4 trigonal pyramids that share  a cornercorner with one Al(3)C4 tetrahedra, corners with three equivalent Si(1)C4 tetrahedra, corners with six equivalent Al(2)C4 trigonal pyramids, and edges with three equivalent Al(1)C4 tetrahedra. The Al(2)-C(2) bond length is 2.21 Å. All Al(2)-C(1) bond lengths are 1.93 Å. In the third Al site, Al(3) is bonded to one C(2) and three equivalent C(4) atoms to form a mixture of distorted edge and corner-sharing AlC4 tetrahedra. The Al(3)-C(2) bond length is 1.92 Å. All Al(3)-C(4) bond lengths are 2.16 Å. In the fourth Al site, Al(4) is bonded to one C(3) and three equivalent C(4) atoms to form AlC4 tetrahedra that share corners with three equivalent Al(3)C4 tetrahedra, corners with three equivalent Si(1)C4 tetrahedra, corners with six equivalent Al(4)C4 tetrahedra, and edges with three equivalent Al(3)C4 tetrahedra. The Al(4)-C(3) bond length is 1.97 Å. All Al(4)-C(4) bond lengths are 2.14 Å. Si(1) is bonded to one C(1) and three equivalent C(3) atoms to form SiC4 tetrahedra that share  a cornercorner with one Al(1)C4 tetrahedra, corners with three equivalent Al(4)C4 tetrahedra, corners with six equivalent Si(1)C4 tetrahedra, and corners with three equivalent Al(2)C4 trigonal pyramids. The Si(1)-C(1) bond length is 1.88 Å. All Si(1)-C(3) bond lengths are 1.99 Å. There are four inequivalent C sites. In the first C site, C(1) is bonded to one Al(1), three equivalent Al(2), and one Si(1) atom to form CAl4Si trigonal bipyramids that share corners with three equivalent C(3)AlSi3 tetrahedra, corners with six equivalent C(1)Al4Si trigonal bipyramids, and edges with three equivalent C(2)Al5 trigonal bipyramids. In the second C site, C(2) is bonded to one Al(2), one Al(3), and three equivalent Al(1) atoms to form distorted CAl5 trigonal bipyramids that share corners with three equivalent C(4)Al6 octahedra, corners with six equivalent C(2)Al5 trigonal bipyramids, and edges with three equivalent C(1)Al4Si trigonal bipyramids. The corner-sharing octahedral tilt angles are 62°. In the third C site, C(3) is bonded to one Al(4) and three equivalent Si(1) atoms to form CAlSi3 tetrahedra that share corners with three equivalent C(4)Al6 octahedra, corners with six equivalent C(3)AlSi3 tetrahedra, and corners with three equivalent C(1)Al4Si trigonal bipyramids. The corner-sharing octahedral tilt angles are 62°. In the fourth C site, C(4) is bonded to three equivalent Al(3) and three equivalent Al(4) atoms to form CAl6 octahedra that share corners with three equivalent C(3)AlSi3 tetrahedra, corners with three equivalent C(2)Al5 trigonal bipyramids, and edges with six equivalent C(4)Al6 octahedra.