La21Fe8Sn7C12 crystallizes in the cubic Fm-3m space group. There are three inequivalent La sites. In the first La site, La(1) is bonded to three equivalent Sn(1) and three equivalent C(1) atoms to form distorted LaSn3C3 octahedra that share corners with six equivalent La(1)Sn3C3 octahedra, edges with three equivalent La(1)Sn3C3 octahedra, and  a faceface with one La(3)Sn6 octahedra. The corner-sharing octahedral tilt angles range from 18-43°. In the second La site, La(2) is bonded in a distorted L-shaped geometry to one Sn(2), two equivalent Sn(1), and two equivalent C(1) atoms. In the third La site, La(3) is bonded to six equivalent Sn(1) atoms to form face-sharing LaSn6 octahedra. Fe(1) is bonded in a trigonal planar geometry to three equivalent C(1) atoms. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 9-coordinate geometry to one La(3), four equivalent La(1), and four equivalent La(2) atoms. In the second Sn site, Sn(2) is bonded to twelve equivalent La(2) atoms to form SnLa12 cuboctahedra that share corners with twenty-four equivalent C(1)La4Fe2 octahedra. The corner-sharing octahedral tilt angles are 44°. C(1) is bonded to two equivalent La(1), two equivalent La(2), and two equivalent Fe(1) atoms to form distorted CLa4Fe2 octahedra that share corners with two equivalent Sn(2)La12 cuboctahedra and edges with five equivalent C(1)La4Fe2 octahedra.
La21Fe8Sn7C12 crystallizes in the cubic Fm-3m space group. There are three inequivalent La sites. In the first La site, La(1) is bonded to three equivalent Sn(1) and three equivalent C(1) atoms to form distorted LaSn3C3 octahedra that share corners with six equivalent La(1)Sn3C3 octahedra, edges with three equivalent La(1)Sn3C3 octahedra, and  a faceface with one La(3)Sn6 octahedra. The corner-sharing octahedral tilt angles range from 18-43°. All La(1)-Sn(1) bond lengths are 3.39 Å. All La(1)-C(1) bond lengths are 2.70 Å. In the second La site, La(2) is bonded in a distorted L-shaped geometry to one Sn(2), two equivalent Sn(1), and two equivalent C(1) atoms. The La(2)-Sn(2) bond length is 3.96 Å. Both La(2)-Sn(1) bond lengths are 3.42 Å. Both La(2)-C(1) bond lengths are 2.60 Å. In the third La site, La(3) is bonded to six equivalent Sn(1) atoms to form face-sharing LaSn6 octahedra. All La(3)-Sn(1) bond lengths are 3.47 Å. Fe(1) is bonded in a trigonal planar geometry to three equivalent C(1) atoms. All Fe(1)-C(1) bond lengths are 1.89 Å. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 9-coordinate geometry to one La(3), four equivalent La(1), and four equivalent La(2) atoms. In the second Sn site, Sn(2) is bonded to twelve equivalent La(2) atoms to form SnLa12 cuboctahedra that share corners with twenty-four equivalent C(1)La4Fe2 octahedra. The corner-sharing octahedral tilt angles are 44°. C(1) is bonded to two equivalent La(1), two equivalent La(2), and two equivalent Fe(1) atoms to form distorted CLa4Fe2 octahedra that share corners with two equivalent Sn(2)La12 cuboctahedra and edges with five equivalent C(1)La4Fe2 octahedra.