Tb4C5 crystallizes in the orthorhombic Pbam space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to one C(2), two equivalent C(1), and two equivalent C(3) atoms to form TbC5 trigonal bipyramids that share corners with two equivalent C(2)Tb5C octahedra, corners with four equivalent Tb(1)C5 trigonal bipyramids, and edges with two equivalent Tb(1)C5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 35-48°. In the second Tb site, Tb(2) is bonded in a 9-coordinate geometry to one C(1), four equivalent C(2), and four equivalent C(3) atoms. There are three inequivalent C sites. In the first C site, C(1) is bonded to two equivalent Tb(2) and four equivalent Tb(1) atoms to form CTb6 octahedra that share corners with four equivalent C(2)Tb5C octahedra, edges with two equivalent C(1)Tb6 octahedra, and edges with four equivalent C(2)Tb5C octahedra. The corner-sharing octahedral tilt angles are 61°. In the second C site, C(2) is bonded to one Tb(1), four equivalent Tb(2), and one C(3) atom to form CTb5C octahedra that share corners with two equivalent C(1)Tb6 octahedra, corners with four equivalent C(2)Tb5C octahedra, corners with two equivalent Tb(1)C5 trigonal bipyramids, edges with two equivalent C(1)Tb6 octahedra, and edges with four equivalent C(2)Tb5C octahedra. The corner-sharing octahedral tilt angles range from 29-61°. In the third C site, C(3) is bonded in a 7-coordinate geometry to two equivalent Tb(1), four equivalent Tb(2), and one C(2) atom.
Tb4C5 crystallizes in the orthorhombic Pbam space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to one C(2), two equivalent C(1), and two equivalent C(3) atoms to form TbC5 trigonal bipyramids that share corners with two equivalent C(2)Tb5C octahedra, corners with four equivalent Tb(1)C5 trigonal bipyramids, and edges with two equivalent Tb(1)C5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 35-48°. The Tb(1)-C(2) bond length is 2.42 Å. Both Tb(1)-C(1) bond lengths are 2.50 Å. There is one shorter (2.61 Å) and one longer (2.71 Å) Tb(1)-C(3) bond length. In the second Tb site, Tb(2) is bonded in a 9-coordinate geometry to one C(1), four equivalent C(2), and four equivalent C(3) atoms. The Tb(2)-C(1) bond length is 2.46 Å. There are two shorter (2.50 Å) and two longer (2.63 Å) Tb(2)-C(2) bond lengths. There are two shorter (2.72 Å) and two longer (2.89 Å) Tb(2)-C(3) bond lengths. There are three inequivalent C sites. In the first C site, C(1) is bonded to two equivalent Tb(2) and four equivalent Tb(1) atoms to form CTb6 octahedra that share corners with four equivalent C(2)Tb5C octahedra, edges with two equivalent C(1)Tb6 octahedra, and edges with four equivalent C(2)Tb5C octahedra. The corner-sharing octahedral tilt angles are 61°. In the second C site, C(2) is bonded to one Tb(1), four equivalent Tb(2), and one C(3) atom to form CTb5C octahedra that share corners with two equivalent C(1)Tb6 octahedra, corners with four equivalent C(2)Tb5C octahedra, corners with two equivalent Tb(1)C5 trigonal bipyramids, edges with two equivalent C(1)Tb6 octahedra, and edges with four equivalent C(2)Tb5C octahedra. The corner-sharing octahedral tilt angles range from 29-61°. The C(2)-C(3) bond length is 1.33 Å. In the third C site, C(3) is bonded in a 7-coordinate geometry to two equivalent Tb(1), four equivalent Tb(2), and one C(2) atom.