La21Fe8C12Sb7 crystallizes in the cubic Fm-3m space group. There are three inequivalent La sites. In the first La site, La(1) is bonded in a 3-coordinate geometry to three equivalent C(1), one Sb(2), and three equivalent Sb(1) atoms. In the second La site, La(2) is bonded in a distorted L-shaped geometry to one La(3), two equivalent C(1), and two equivalent Sb(1) atoms. In the third La site, La(3) is bonded to twelve equivalent La(2) atoms to form LaLa12 cuboctahedra that share corners with twenty-four equivalent C(1)La4Fe2 octahedra. The corner-sharing octahedral tilt angles are 45°. Fe(1) is bonded in a trigonal planar geometry to three equivalent C(1) atoms. 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 La(3)La12 cuboctahedra and edges with five equivalent C(1)La4Fe2 octahedra. There are two inequivalent Sb sites. In the first Sb site, Sb(1) is bonded in a 8-coordinate geometry to four equivalent La(1) and four equivalent La(2) atoms. In the second Sb site, Sb(2) is bonded in a body-centered cubic geometry to eight equivalent La(1) atoms.
La21Fe8C12Sb7 crystallizes in the cubic Fm-3m space group. There are three inequivalent La sites. In the first La site, La(1) is bonded in a 3-coordinate geometry to three equivalent C(1), one Sb(2), and three equivalent Sb(1) atoms. All La(1)-C(1) bond lengths are 2.75 Å. The La(1)-Sb(2) bond length is 3.79 Å. All La(1)-Sb(1) bond lengths are 3.45 Å. In the second La site, La(2) is bonded in a distorted L-shaped geometry to one La(3), two equivalent C(1), and two equivalent Sb(1) atoms. The La(2)-La(3) bond length is 4.01 Å. Both La(2)-C(1) bond lengths are 2.56 Å. Both La(2)-Sb(1) bond lengths are 3.30 Å. In the third La site, La(3) is bonded to twelve equivalent La(2) atoms to form LaLa12 cuboctahedra that share corners with twenty-four equivalent C(1)La4Fe2 octahedra. The corner-sharing octahedral tilt angles are 45°. 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. 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 La(3)La12 cuboctahedra and edges with five equivalent C(1)La4Fe2 octahedra. There are two inequivalent Sb sites. In the first Sb site, Sb(1) is bonded in a 8-coordinate geometry to four equivalent La(1) and four equivalent La(2) atoms. In the second Sb site, Sb(2) is bonded in a body-centered cubic geometry to eight equivalent La(1) atoms.