Ho2Co7 crystallizes in the trigonal R-3m space group. There are six inequivalent Ho sites. In the first Ho site, Ho(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 Ho site, Ho(1) is bonded in a 18-coordinate geometry to three equivalent Co(2), three equivalent Co(3), six equivalent Co(4), and six equivalent Co(5) atoms. In the third Ho site, Ho(2) is bonded in a 12-coordinate geometry to three equivalent Co(1) and nine equivalent Co(5) atoms. In the fourth Ho site, Ho(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 Ho site, Ho(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 Ho site, Ho(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 nine inequivalent Co sites. In the first Co site, Co(4) is bonded to four Ho(1,1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoHo4Co8 cuboctahedra that share corners with four equivalent Co(4)Ho4Co8 cuboctahedra; corners with twelve equivalent Co(5)Ho5Co7 cuboctahedra; edges with two equivalent Co(4)Ho4Co8 cuboctahedra; edges with eight equivalent Co(5)Ho5Co7 cuboctahedra; faces with two equivalent Co(5)Ho5Co7 cuboctahedra; and faces with eight Co(4,4)Ho4Co8 cuboctahedra. In the second Co site, Co(4) is bonded to four Ho(1,1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoHo4Co8 cuboctahedra that share corners with four equivalent Co(4)Ho4Co8 cuboctahedra; corners with twelve equivalent Co(5)Ho5Co7 cuboctahedra; edges with two equivalent Co(4)Ho4Co8 cuboctahedra; edges with eight equivalent Co(5)Ho5Co7 cuboctahedra; faces with two equivalent Co(5)Ho5Co7 cuboctahedra; and faces with eight Co(4,4)Ho4Co8 cuboctahedra. In the third Co site, Co(1) is bonded to six equivalent Ho(2) and six equivalent Co(5) atoms to form CoHo6Co6 cuboctahedra that share corners with twelve equivalent Co(5)Ho5Co7 cuboctahedra, edges with six equivalent Co(1)Ho6Co6 cuboctahedra, and faces with eighteen equivalent Co(5)Ho5Co7 cuboctahedra. In the fourth Co site, Co(2) is bonded in a 9-coordinate geometry to three equivalent Ho(1), three equivalent Co(4), and three equivalent Co(5) atoms. In the fifth Co site, Co(4) is bonded to four Ho(1,1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoHo4Co8 cuboctahedra that share corners with four equivalent Co(4)Ho4Co8 cuboctahedra; corners with twelve equivalent Co(5)Ho5Co7 cuboctahedra; edges with two equivalent Co(4)Ho4Co8 cuboctahedra; edges with eight equivalent Co(5)Ho5Co7 cuboctahedra; faces with two equivalent Co(5)Ho5Co7 cuboctahedra; and faces with eight Co(4,4)Ho4Co8 cuboctahedra. In the sixth Co site, Co(3) is bonded in a 9-coordinate geometry to three equivalent Ho(1); three Co(4,4,4); and three equivalent Co(5) atoms. In the seventh Co site, Co(4) is bonded to four Ho(1,1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoHo4Co8 cuboctahedra that share corners with four equivalent Co(4)Ho4Co8 cuboctahedra; corners with twelve equivalent Co(5)Ho5Co7 cuboctahedra; edges with two equivalent Co(4)Ho4Co8 cuboctahedra; edges with eight equivalent Co(5)Ho5Co7 cuboctahedra; faces with two equivalent Co(5)Ho5Co7 cuboctahedra; and faces with eight Co(4,4)Ho4Co8 cuboctahedra. In the eighth Co site, Co(4) is bonded to four equivalent Ho(1), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(4) atoms to form CoHo4Co8 cuboctahedra that share corners with four equivalent Co(4)Ho4Co8 cuboctahedra, corners with twelve equivalent Co(5)Ho5Co7 cuboctahedra, edges with two equivalent Co(4)Ho4Co8 cuboctahedra, edges with eight equivalent Co(5)Ho5Co7 cuboctahedra, faces with two equivalent Co(5)Ho5Co7 cuboctahedra, and faces with eight equivalent Co(4)Ho4Co8 cuboctahedra. In the ninth Co site, Co(5) is bonded to two equivalent Ho(1), three equivalent Ho(2), one Co(1), one Co(2), one Co(3), and four equivalent Co(5) atoms to form distorted CoHo5Co7 cuboctahedra that share corners with two equivalent Co(1)Ho6Co6 cuboctahedra; corners with six Co(4,4,4)Ho4Co8 cuboctahedra; corners with nine equivalent Co(5)Ho5Co7 cuboctahedra; edges with four Co(4,4)Ho4Co8 cuboctahedra; edges with four equivalent Co(5)Ho5Co7 cuboctahedra;  a faceface with one Co(4)Ho4Co8 cuboctahedra; faces with three equivalent Co(1)Ho6Co6 cuboctahedra; and faces with ten equivalent Co(5)Ho5Co7 cuboctahedra.
Ho2Co7 crystallizes in the trigonal R-3m space group. There are six inequivalent Ho sites. In the first Ho site, Ho(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 Ho(1)-Co(2) bond lengths are 2.84 Å. All Ho(1)-Co(3) bond lengths are 2.84 Å. All Ho(1)-Co(4,4,4) bond lengths are 3.10 Å. All Ho(1)-Co(5) bond lengths are 3.20 Å. In the second Ho site, Ho(1) is bonded in a 18-coordinate geometry to three equivalent Co(2), three equivalent Co(3), six equivalent Co(4), and six equivalent Co(5) atoms. All Ho(1)-Co(2) bond lengths are 2.84 Å. All Ho(1)-Co(3) bond lengths are 2.84 Å. All Ho(1)-Co(4) bond lengths are 3.10 Å. All Ho(1)-Co(5) bond lengths are 3.20 Å. In the third Ho site, Ho(2) is bonded in a 12-coordinate geometry to three equivalent Co(1) and nine equivalent Co(5) atoms. All Ho(2)-Co(1) bond lengths are 2.92 Å. There are six shorter (2.83 Å) and three longer (3.06 Å) Ho(2)-Co(5) bond lengths. In the fourth Ho site, Ho(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 Ho(1)-Co(2) bond lengths are 2.84 Å. All Ho(1)-Co(3) bond lengths are 2.84 Å. All Ho(1)-Co(4,4,4) bond lengths are 3.10 Å. All Ho(1)-Co(5) bond lengths are 3.20 Å. In the fifth Ho site, Ho(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 Ho(1)-Co(2) bond lengths are 2.84 Å. All Ho(1)-Co(3) bond lengths are 2.84 Å. All Ho(1)-Co(4,4,4) bond lengths are 3.10 Å. All Ho(1)-Co(5) bond lengths are 3.20 Å. In the sixth Ho site, Ho(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 Ho(1)-Co(2) bond lengths are 2.84 Å. All Ho(1)-Co(3) bond lengths are 2.84 Å. All Ho(1)-Co(4,4,4) bond lengths are 3.10 Å. All Ho(1)-Co(5) bond lengths are 3.20 Å. There are nine inequivalent Co sites. In the first Co site, Co(4) is bonded to four Ho(1,1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoHo4Co8 cuboctahedra that share corners with four equivalent Co(4)Ho4Co8 cuboctahedra; corners with twelve equivalent Co(5)Ho5Co7 cuboctahedra; edges with two equivalent Co(4)Ho4Co8 cuboctahedra; edges with eight equivalent Co(5)Ho5Co7 cuboctahedra; faces with two equivalent Co(5)Ho5Co7 cuboctahedra; and faces with eight Co(4,4)Ho4Co8 cuboctahedra. Both Co(4)-Co(2) bond lengths are 2.43 Å. Both Co(4)-Co(3) bond lengths are 2.44 Å. All Co(4)-Co(4,4) bond lengths are 2.46 Å. In the second Co site, Co(4) is bonded to four Ho(1,1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoHo4Co8 cuboctahedra that share corners with four equivalent Co(4)Ho4Co8 cuboctahedra; corners with twelve equivalent Co(5)Ho5Co7 cuboctahedra; edges with two equivalent Co(4)Ho4Co8 cuboctahedra; edges with eight equivalent Co(5)Ho5Co7 cuboctahedra; faces with two equivalent Co(5)Ho5Co7 cuboctahedra; and faces with eight Co(4,4)Ho4Co8 cuboctahedra. Both Co(4)-Co(2) bond lengths are 2.43 Å. Both Co(4)-Co(3) bond lengths are 2.44 Å. Both Co(4)-Co(4) bond lengths are 2.46 Å. In the third Co site, Co(1) is bonded to six equivalent Ho(2) and six equivalent Co(5) atoms to form CoHo6Co6 cuboctahedra that share corners with twelve equivalent Co(5)Ho5Co7 cuboctahedra, edges with six equivalent Co(1)Ho6Co6 cuboctahedra, and faces with eighteen equivalent Co(5)Ho5Co7 cuboctahedra. All Co(1)-Co(5) bond lengths are 2.50 Å. In the fourth Co site, Co(2) is bonded in a 9-coordinate geometry to three equivalent Ho(1), three equivalent Co(4), and three equivalent Co(5) atoms. All Co(2)-Co(4) bond lengths are 2.43 Å. All Co(2)-Co(5) bond lengths are 2.42 Å. In the fifth Co site, Co(4) is bonded to four Ho(1,1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoHo4Co8 cuboctahedra that share corners with four equivalent Co(4)Ho4Co8 cuboctahedra; corners with twelve equivalent Co(5)Ho5Co7 cuboctahedra; edges with two equivalent Co(4)Ho4Co8 cuboctahedra; edges with eight equivalent Co(5)Ho5Co7 cuboctahedra; faces with two equivalent Co(5)Ho5Co7 cuboctahedra; and faces with eight Co(4,4)Ho4Co8 cuboctahedra. Both Co(4)-Co(2) bond lengths are 2.43 Å. Both Co(4)-Co(3) bond lengths are 2.44 Å. All Co(4)-Co(4,4) bond lengths are 2.46 Å. In the sixth Co site, Co(3) is bonded in a 9-coordinate geometry to three equivalent Ho(1); three Co(4,4,4); and three equivalent Co(5) atoms. The Co(3)-Co(4) bond length is 2.44 Å. All Co(3)-Co(5) bond lengths are 2.41 Å. In the seventh Co site, Co(4) is bonded to four Ho(1,1); two equivalent Co(2); two equivalent Co(3); and four Co(4,4) atoms to form CoHo4Co8 cuboctahedra that share corners with four equivalent Co(4)Ho4Co8 cuboctahedra; corners with twelve equivalent Co(5)Ho5Co7 cuboctahedra; edges with two equivalent Co(4)Ho4Co8 cuboctahedra; edges with eight equivalent Co(5)Ho5Co7 cuboctahedra; faces with two equivalent Co(5)Ho5Co7 cuboctahedra; and faces with eight Co(4,4)Ho4Co8 cuboctahedra. Both Co(4)-Co(2) bond lengths are 2.43 Å. Both Co(4)-Co(4) bond lengths are 2.46 Å. In the eighth Co site, Co(4) is bonded to four equivalent Ho(1), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(4) atoms to form CoHo4Co8 cuboctahedra that share corners with four equivalent Co(4)Ho4Co8 cuboctahedra, corners with twelve equivalent Co(5)Ho5Co7 cuboctahedra, edges with two equivalent Co(4)Ho4Co8 cuboctahedra, edges with eight equivalent Co(5)Ho5Co7 cuboctahedra, faces with two equivalent Co(5)Ho5Co7 cuboctahedra, and faces with eight equivalent Co(4)Ho4Co8 cuboctahedra. Both Co(4)-Co(3) bond lengths are 2.44 Å. All Co(4)-Co(4) bond lengths are 2.46 Å. In the ninth Co site, Co(5) is bonded to two equivalent Ho(1), three equivalent Ho(2), one Co(1), one Co(2), one Co(3), and four equivalent Co(5) atoms to form distorted CoHo5Co7 cuboctahedra that share corners with two equivalent Co(1)Ho6Co6 cuboctahedra; corners with six Co(4,4,4)Ho4Co8 cuboctahedra; corners with nine equivalent Co(5)Ho5Co7 cuboctahedra; edges with four Co(4,4)Ho4Co8 cuboctahedra; edges with four equivalent Co(5)Ho5Co7 cuboctahedra;  a faceface with one Co(4)Ho4Co8 cuboctahedra; faces with three equivalent Co(1)Ho6Co6 cuboctahedra; and faces with ten equivalent Co(5)Ho5Co7 cuboctahedra. All Co(5)-Co(5) bond lengths are 2.46 Å.