Ho3Co8Sn4 is Hexagonal Laves-derived structured and crystallizes in the hexagonal P6_3mc space group. Ho(1) is bonded in a 12-coordinate geometry to two equivalent Co(1), two equivalent Co(2), two equivalent Co(3), two equivalent Sn(1), and four equivalent Sn(2) atoms. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a 10-coordinate geometry to six equivalent Ho(1), one Sn(1), and three equivalent Sn(2) atoms. In the second Co site, Co(2) is bonded to two equivalent Ho(1), two equivalent Co(2), two equivalent Co(4), three equivalent Co(3), and three equivalent Sn(2) atoms to form distorted CoHo2Co7Sn3 cuboctahedra that share corners with four equivalent Co(2)Ho2Co7Sn3 cuboctahedra, corners with five equivalent Sn(2)Ho4Co8 cuboctahedra, faces with two equivalent Co(4)Co9Sn3 cuboctahedra, faces with six equivalent Co(2)Ho2Co7Sn3 cuboctahedra, and faces with six equivalent Sn(2)Ho4Co8 cuboctahedra. In the third Co site, Co(3) is bonded in a 10-coordinate geometry to two equivalent Ho(1), one Co(4), three equivalent Co(2), one Sn(1), and three equivalent Sn(2) atoms. In the fourth Co site, Co(4) is bonded to three equivalent Co(3), six equivalent Co(2), and three equivalent Sn(2) atoms to form CoCo9Sn3 cuboctahedra that share corners with three equivalent Sn(2)Ho4Co8 cuboctahedra, faces with two equivalent Co(4)Co9Sn3 cuboctahedra, faces with six equivalent Co(2)Ho2Co7Sn3 cuboctahedra, and faces with six equivalent Sn(2)Ho4Co8 cuboctahedra. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 10-coordinate geometry to six equivalent Ho(1), one Co(1), and three equivalent Co(3) atoms. In the second Sn site, Sn(2) is bonded to four equivalent Ho(1), one Co(1), one Co(4), three equivalent Co(2), and three equivalent Co(3) atoms to form distorted SnHo4Co8 cuboctahedra that share  a cornercorner with one Co(4)Co9Sn3 cuboctahedra, corners with four equivalent Sn(2)Ho4Co8 cuboctahedra, corners with five equivalent Co(2)Ho2Co7Sn3 cuboctahedra, faces with two equivalent Co(4)Co9Sn3 cuboctahedra, faces with six equivalent Co(2)Ho2Co7Sn3 cuboctahedra, and faces with eight equivalent Sn(2)Ho4Co8 cuboctahedra.
Ho3Co8Sn4 is Hexagonal Laves-derived structured and crystallizes in the hexagonal P6_3mc space group. Ho(1) is bonded in a 12-coordinate geometry to two equivalent Co(1), two equivalent Co(2), two equivalent Co(3), two equivalent Sn(1), and four equivalent Sn(2) atoms. There is one shorter (3.15 Å) and one longer (3.38 Å) Ho(1)-Co(1) bond length. Both Ho(1)-Co(2) bond lengths are 3.13 Å. Both Ho(1)-Co(3) bond lengths are 3.03 Å. There is one shorter (3.17 Å) and one longer (3.27 Å) Ho(1)-Sn(1) bond length. There are two shorter (3.16 Å) and two longer (3.19 Å) Ho(1)-Sn(2) bond lengths. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a 10-coordinate geometry to six equivalent Ho(1), one Sn(1), and three equivalent Sn(2) atoms. The Co(1)-Sn(1) bond length is 2.65 Å. All Co(1)-Sn(2) bond lengths are 2.51 Å. In the second Co site, Co(2) is bonded to two equivalent Ho(1), two equivalent Co(2), two equivalent Co(4), three equivalent Co(3), and three equivalent Sn(2) atoms to form distorted CoHo2Co7Sn3 cuboctahedra that share corners with four equivalent Co(2)Ho2Co7Sn3 cuboctahedra, corners with five equivalent Sn(2)Ho4Co8 cuboctahedra, faces with two equivalent Co(4)Co9Sn3 cuboctahedra, faces with six equivalent Co(2)Ho2Co7Sn3 cuboctahedra, and faces with six equivalent Sn(2)Ho4Co8 cuboctahedra. Both Co(2)-Co(2) bond lengths are 2.62 Å. There is one shorter (2.37 Å) and one longer (2.47 Å) Co(2)-Co(4) bond length. There is one shorter (2.55 Å) and two longer (2.56 Å) Co(2)-Co(3) bond lengths. There is one shorter (2.64 Å) and two longer (2.66 Å) Co(2)-Sn(2) bond lengths. In the third Co site, Co(3) is bonded in a 10-coordinate geometry to two equivalent Ho(1), one Co(4), three equivalent Co(2), one Sn(1), and three equivalent Sn(2) atoms. The Co(3)-Co(4) bond length is 2.48 Å. The Co(3)-Sn(1) bond length is 2.65 Å. There are two shorter (2.72 Å) and one longer (2.79 Å) Co(3)-Sn(2) bond length. In the fourth Co site, Co(4) is bonded to three equivalent Co(3), six equivalent Co(2), and three equivalent Sn(2) atoms to form CoCo9Sn3 cuboctahedra that share corners with three equivalent Sn(2)Ho4Co8 cuboctahedra, faces with two equivalent Co(4)Co9Sn3 cuboctahedra, faces with six equivalent Co(2)Ho2Co7Sn3 cuboctahedra, and faces with six equivalent Sn(2)Ho4Co8 cuboctahedra. All Co(4)-Sn(2) bond lengths are 2.67 Å. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 10-coordinate geometry to six equivalent Ho(1), one Co(1), and three equivalent Co(3) atoms. In the second Sn site, Sn(2) is bonded to four equivalent Ho(1), one Co(1), one Co(4), three equivalent Co(2), and three equivalent Co(3) atoms to form distorted SnHo4Co8 cuboctahedra that share  a cornercorner with one Co(4)Co9Sn3 cuboctahedra, corners with four equivalent Sn(2)Ho4Co8 cuboctahedra, corners with five equivalent Co(2)Ho2Co7Sn3 cuboctahedra, faces with two equivalent Co(4)Co9Sn3 cuboctahedra, faces with six equivalent Co(2)Ho2Co7Sn3 cuboctahedra, and faces with eight equivalent Sn(2)Ho4Co8 cuboctahedra.