La2Co7 crystallizes in the trigonal R-3m space group. There are six inequivalent La sites. In the first La site, La(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4,4); and six equivalent Co(5) atoms. In the second La site, La(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4); and six equivalent Co(5) atoms. In the third La site, La(2) is bonded in a 12-coordinate geometry to three equivalent Co(1) and nine equivalent Co(5) atoms. In the fourth La site, La(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4,4); and six equivalent Co(5) atoms. In the fifth La site, La(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4,4); and six equivalent Co(5) atoms. In the sixth La site, La(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4,4); and six equivalent Co(5) atoms. There are eight inequivalent Co sites. In the first Co site, Co(4) is bonded to four La(1,1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoLa4Co8 cuboctahedra that share corners with four equivalent Co(4)La4Co8 cuboctahedra; corners with twelve equivalent Co(5)La5Co7 cuboctahedra; edges with two equivalent Co(4)La4Co8 cuboctahedra; edges with eight equivalent Co(5)La5Co7 cuboctahedra; faces with two equivalent Co(5)La5Co7 cuboctahedra; and faces with eight Co(4,4)La4Co8 cuboctahedra. In the second Co site, Co(4) is bonded to four La(1,1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoLa4Co8 cuboctahedra that share corners with four equivalent Co(4)La4Co8 cuboctahedra; corners with twelve equivalent Co(5)La5Co7 cuboctahedra; edges with two equivalent Co(4)La4Co8 cuboctahedra; edges with eight equivalent Co(5)La5Co7 cuboctahedra; faces with two equivalent Co(5)La5Co7 cuboctahedra; and faces with eight Co(4,4)La4Co8 cuboctahedra. In the third Co site, Co(1) is bonded to six equivalent La(2) and six equivalent Co(5) atoms to form CoLa6Co6 cuboctahedra that share corners with twelve equivalent Co(5)La5Co7 cuboctahedra, edges with six equivalent Co(1)La6Co6 cuboctahedra, and faces with eighteen equivalent Co(5)La5Co7 cuboctahedra. In the fourth Co site, Co(2) is bonded in a 9-coordinate geometry to three equivalent La(1); three Co(4,4); and three equivalent Co(5) atoms. In the fifth Co site, Co(3) is bonded in a 9-coordinate geometry to three equivalent La(1); three Co(4,4,4); and three equivalent Co(5) atoms. In the sixth Co site, Co(4) is bonded to four equivalent La(1), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(4) atoms to form CoLa4Co8 cuboctahedra that share corners with four equivalent Co(4)La4Co8 cuboctahedra, corners with twelve equivalent Co(5)La5Co7 cuboctahedra, edges with two equivalent Co(4)La4Co8 cuboctahedra, edges with eight equivalent Co(5)La5Co7 cuboctahedra, faces with two equivalent Co(5)La5Co7 cuboctahedra, and faces with eight equivalent Co(4)La4Co8 cuboctahedra. In the seventh Co site, Co(4) is bonded to four equivalent La(1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoLa4Co8 cuboctahedra that share corners with four equivalent Co(4)La4Co8 cuboctahedra; corners with twelve equivalent Co(5)La5Co7 cuboctahedra; edges with two equivalent Co(4)La4Co8 cuboctahedra; edges with eight equivalent Co(5)La5Co7 cuboctahedra; faces with two equivalent Co(5)La5Co7 cuboctahedra; and faces with eight Co(4,4)La4Co8 cuboctahedra. In the eighth Co site, Co(5) is bonded to two equivalent La(1), three equivalent La(2), one Co(1), one Co(2), one Co(3), and four equivalent Co(5) atoms to form distorted CoLa5Co7 cuboctahedra that share corners with two equivalent Co(1)La6Co6 cuboctahedra; corners with six Co(4,4,4)La4Co8 cuboctahedra; corners with nine equivalent Co(5)La5Co7 cuboctahedra; edges with four Co(4,4)La4Co8 cuboctahedra; edges with four equivalent Co(5)La5Co7 cuboctahedra;  a faceface with one Co(4)La4Co8 cuboctahedra; faces with three equivalent Co(1)La6Co6 cuboctahedra; and faces with ten equivalent Co(5)La5Co7 cuboctahedra.
La2Co7 crystallizes in the trigonal R-3m space group. There are six inequivalent La sites. In the first La site, La(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4,4); and six equivalent Co(5) atoms. All La(1)-Co(2) bond lengths are 2.91 Å. All La(1)-Co(3) bond lengths are 2.91 Å. All La(1)-Co(4,4,4) bond lengths are 3.16 Å. All La(1)-Co(5) bond lengths are 3.26 Å. In the second La site, La(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4); and six equivalent Co(5) atoms. All La(1)-Co(2) bond lengths are 2.91 Å. All La(1)-Co(3) bond lengths are 2.91 Å. All La(1)-Co(4,4) bond lengths are 3.16 Å. All La(1)-Co(5) bond lengths are 3.26 Å. In the third La site, La(2) is bonded in a 12-coordinate geometry to three equivalent Co(1) and nine equivalent Co(5) atoms. All La(2)-Co(1) bond lengths are 2.98 Å. There are six shorter (2.94 Å) and three longer (3.23 Å) La(2)-Co(5) bond lengths. In the fourth La site, La(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4,4); and six equivalent Co(5) atoms. All La(1)-Co(2) bond lengths are 2.91 Å. All La(1)-Co(3) bond lengths are 2.91 Å. All La(1)-Co(4,4,4) bond lengths are 3.16 Å. All La(1)-Co(5) bond lengths are 3.26 Å. In the fifth La site, La(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4,4); and six equivalent Co(5) atoms. All La(1)-Co(2) bond lengths are 2.91 Å. All La(1)-Co(3) bond lengths are 2.91 Å. All La(1)-Co(4,4,4) bond lengths are 3.16 Å. All La(1)-Co(5) bond lengths are 3.26 Å. In the sixth La site, La(1) is bonded in a 18-coordinate geometry to three equivalent Co(2); three equivalent Co(3); six Co(4,4,4); and six equivalent Co(5) atoms. All La(1)-Co(2) bond lengths are 2.91 Å. All La(1)-Co(3) bond lengths are 2.91 Å. All La(1)-Co(4,4,4) bond lengths are 3.16 Å. All La(1)-Co(5) bond lengths are 3.26 Å. There are eight inequivalent Co sites. In the first Co site, Co(4) is bonded to four La(1,1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoLa4Co8 cuboctahedra that share corners with four equivalent Co(4)La4Co8 cuboctahedra; corners with twelve equivalent Co(5)La5Co7 cuboctahedra; edges with two equivalent Co(4)La4Co8 cuboctahedra; edges with eight equivalent Co(5)La5Co7 cuboctahedra; faces with two equivalent Co(5)La5Co7 cuboctahedra; and faces with eight Co(4,4)La4Co8 cuboctahedra. Both Co(4)-Co(2) bond lengths are 2.50 Å. Both Co(4)-Co(3) bond lengths are 2.48 Å. All Co(4)-Co(4,4) bond lengths are 2.52 Å. In the second Co site, Co(4) is bonded to four La(1,1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoLa4Co8 cuboctahedra that share corners with four equivalent Co(4)La4Co8 cuboctahedra; corners with twelve equivalent Co(5)La5Co7 cuboctahedra; edges with two equivalent Co(4)La4Co8 cuboctahedra; edges with eight equivalent Co(5)La5Co7 cuboctahedra; faces with two equivalent Co(5)La5Co7 cuboctahedra; and faces with eight Co(4,4)La4Co8 cuboctahedra. Both Co(4)-Co(2) bond lengths are 2.50 Å. Both Co(4)-Co(3) bond lengths are 2.48 Å. Both Co(4)-Co(4) bond lengths are 2.52 Å. In the third Co site, Co(1) is bonded to six equivalent La(2) and six equivalent Co(5) atoms to form CoLa6Co6 cuboctahedra that share corners with twelve equivalent Co(5)La5Co7 cuboctahedra, edges with six equivalent Co(1)La6Co6 cuboctahedra, and faces with eighteen equivalent Co(5)La5Co7 cuboctahedra. All Co(1)-Co(5) bond lengths are 2.63 Å. In the fourth Co site, Co(2) is bonded in a 9-coordinate geometry to three equivalent La(1); three Co(4,4); and three equivalent Co(5) atoms. All Co(2)-Co(4,4) bond lengths are 2.50 Å. All Co(2)-Co(5) bond lengths are 2.43 Å. In the fifth Co site, Co(3) is bonded in a 9-coordinate geometry to three equivalent La(1); three Co(4,4,4); and three equivalent Co(5) atoms. The Co(3)-Co(4) bond length is 2.48 Å. All Co(3)-Co(5) bond lengths are 2.45 Å. In the sixth Co site, Co(4) is bonded to four equivalent La(1), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(4) atoms to form CoLa4Co8 cuboctahedra that share corners with four equivalent Co(4)La4Co8 cuboctahedra, corners with twelve equivalent Co(5)La5Co7 cuboctahedra, edges with two equivalent Co(4)La4Co8 cuboctahedra, edges with eight equivalent Co(5)La5Co7 cuboctahedra, faces with two equivalent Co(5)La5Co7 cuboctahedra, and faces with eight equivalent Co(4)La4Co8 cuboctahedra. Both Co(4)-Co(3) bond lengths are 2.48 Å. All Co(4)-Co(4) bond lengths are 2.52 Å. In the seventh Co site, Co(4) is bonded to four equivalent La(1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoLa4Co8 cuboctahedra that share corners with four equivalent Co(4)La4Co8 cuboctahedra; corners with twelve equivalent Co(5)La5Co7 cuboctahedra; edges with two equivalent Co(4)La4Co8 cuboctahedra; edges with eight equivalent Co(5)La5Co7 cuboctahedra; faces with two equivalent Co(5)La5Co7 cuboctahedra; and faces with eight Co(4,4)La4Co8 cuboctahedra. Both Co(4)-Co(4) bond lengths are 2.52 Å. In the eighth Co site, Co(5) is bonded to two equivalent La(1), three equivalent La(2), one Co(1), one Co(2), one Co(3), and four equivalent Co(5) atoms to form distorted CoLa5Co7 cuboctahedra that share corners with two equivalent Co(1)La6Co6 cuboctahedra; corners with six Co(4,4,4)La4Co8 cuboctahedra; corners with nine equivalent Co(5)La5Co7 cuboctahedra; edges with four Co(4,4)La4Co8 cuboctahedra; edges with four equivalent Co(5)La5Co7 cuboctahedra;  a faceface with one Co(4)La4Co8 cuboctahedra; faces with three equivalent Co(1)La6Co6 cuboctahedra; and faces with ten equivalent Co(5)La5Co7 cuboctahedra. There are two shorter (2.49 Å) and two longer (2.54 Å) Co(5)-Co(5) bond lengths.