Al8BC5 is Aluminum carbonitride-like structured and crystallizes in the trigonal R-3m 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(3) atoms to form a mixture of distorted edge and corner-sharing AlC4 tetrahedra. In the second Al site, Al(2) is bonded to three equivalent B(1) and one C(2) atom to form distorted AlB3C tetrahedra that share corners with nine equivalent Al(2)B3C tetrahedra,  a cornercorner with one Al(4)C4 trigonal pyramid, corners with three equivalent Al(3)C4 trigonal pyramids, and edges with three equivalent Al(2)B3C tetrahedra. In the third Al site, Al(3) is bonded to one C(1) and three equivalent C(2) atoms to form AlC4 trigonal pyramids that share  a cornercorner with one Al(1)C4 tetrahedra, corners with three equivalent Al(2)B3C tetrahedra, corners with six equivalent Al(3)C4 trigonal pyramids, and edges with three equivalent Al(4)C4 trigonal pyramids. In the fourth Al site, Al(4) 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(2)B3C tetrahedra, corners with three equivalent Al(1)C4 tetrahedra, corners with six equivalent Al(4)C4 trigonal pyramids, and edges with three equivalent Al(3)C4 trigonal pyramids. B(1) is bonded to six equivalent Al(2) atoms to form BAl6 octahedra that share corners with six equivalent C(2)Al5 trigonal bipyramids and edges with six equivalent B(1)Al6 octahedra. There are three inequivalent C sites. In the first C site, C(1) is bonded to one Al(1), one Al(3), and three equivalent Al(4) atoms to form distorted CAl5 trigonal bipyramids that share corners with three equivalent C(3)Al6 octahedra, corners with six equivalent C(1)Al5 trigonal bipyramids, and edges with three equivalent C(2)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 63°. In the second C site, C(2) is bonded to one Al(2), one Al(4), and three equivalent Al(3) atoms to form CAl5 trigonal bipyramids that share corners with three equivalent B(1)Al6 octahedra, corners with six equivalent C(2)Al5 trigonal bipyramids, and edges with three equivalent C(1)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 62°. In the third C site, C(3) is bonded to six equivalent Al(1) atoms to form CAl6 octahedra that share corners with six equivalent C(1)Al5 trigonal bipyramids and edges with six equivalent C(3)Al6 octahedra.
Al8BC5 is Aluminum carbonitride-like structured and crystallizes in the trigonal R-3m 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(3) atoms to form a mixture of distorted edge and corner-sharing AlC4 tetrahedra. The Al(1)-C(1) bond length is 1.93 Å. All Al(1)-C(3) bond lengths are 2.20 Å. In the second Al site, Al(2) is bonded to three equivalent B(1) and one C(2) atom to form distorted AlB3C tetrahedra that share corners with nine equivalent Al(2)B3C tetrahedra,  a cornercorner with one Al(4)C4 trigonal pyramid, corners with three equivalent Al(3)C4 trigonal pyramids, and edges with three equivalent Al(2)B3C tetrahedra. All Al(2)-B(1) bond lengths are 2.21 Å. The Al(2)-C(2) bond length is 1.96 Å. In the third Al site, Al(3) is bonded to one C(1) and three equivalent C(2) atoms to form AlC4 trigonal pyramids that share  a cornercorner with one Al(1)C4 tetrahedra, corners with three equivalent Al(2)B3C tetrahedra, corners with six equivalent Al(3)C4 trigonal pyramids, and edges with three equivalent Al(4)C4 trigonal pyramids. The Al(3)-C(1) bond length is 2.23 Å. All Al(3)-C(2) bond lengths are 1.97 Å. In the fourth Al site, Al(4) 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(2)B3C tetrahedra, corners with three equivalent Al(1)C4 tetrahedra, corners with six equivalent Al(4)C4 trigonal pyramids, and edges with three equivalent Al(3)C4 trigonal pyramids. The Al(4)-C(2) bond length is 2.14 Å. All Al(4)-C(1) bond lengths are 1.99 Å. B(1) is bonded to six equivalent Al(2) atoms to form BAl6 octahedra that share corners with six equivalent C(2)Al5 trigonal bipyramids and edges with six equivalent B(1)Al6 octahedra. There are three inequivalent C sites. In the first C site, C(1) is bonded to one Al(1), one Al(3), and three equivalent Al(4) atoms to form distorted CAl5 trigonal bipyramids that share corners with three equivalent C(3)Al6 octahedra, corners with six equivalent C(1)Al5 trigonal bipyramids, and edges with three equivalent C(2)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 63°. In the second C site, C(2) is bonded to one Al(2), one Al(4), and three equivalent Al(3) atoms to form CAl5 trigonal bipyramids that share corners with three equivalent B(1)Al6 octahedra, corners with six equivalent C(2)Al5 trigonal bipyramids, and edges with three equivalent C(1)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 62°. In the third C site, C(3) is bonded to six equivalent Al(1) atoms to form CAl6 octahedra that share corners with six equivalent C(1)Al5 trigonal bipyramids and edges with six equivalent C(3)Al6 octahedra.