Ho2Mo2C3 crystallizes in the monoclinic C2/m space group. Ho(1) is bonded in a 5-coordinate geometry to two equivalent C(1) and three equivalent C(2) atoms. Mo(1) is bonded to one C(1) and three equivalent C(2) atoms to form a mixture of corner and edge-sharing MoC4 trigonal pyramids. There are two inequivalent C sites. In the first C site, C(1) is bonded to four equivalent Ho(1) and two equivalent Mo(1) atoms to form CHo4Mo2 octahedra that share corners with twelve equivalent C(2)Ho3Mo3 octahedra, edges with two equivalent C(1)Ho4Mo2 octahedra, and faces with two equivalent C(2)Ho3Mo3 octahedra. The corner-sharing octahedral tilt angles range from 43-57°. In the second C site, C(2) is bonded to three equivalent Ho(1) and three equivalent Mo(1) atoms to form CHo3Mo3 octahedra that share corners with six equivalent C(1)Ho4Mo2 octahedra, edges with six equivalent C(2)Ho3Mo3 octahedra, and  a faceface with one C(1)Ho4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 43-57°.
Ho2Mo2C3 crystallizes in the monoclinic C2/m space group. Ho(1) is bonded in a 5-coordinate geometry to two equivalent C(1) and three equivalent C(2) atoms. Both Ho(1)-C(1) bond lengths are 2.51 Å. There is one shorter (2.40 Å) and two longer (2.57 Å) Ho(1)-C(2) bond lengths. Mo(1) is bonded to one C(1) and three equivalent C(2) atoms to form a mixture of corner and edge-sharing MoC4 trigonal pyramids. The Mo(1)-C(1) bond length is 2.02 Å. There are two shorter (2.10 Å) and one longer (2.11 Å) Mo(1)-C(2) bond length. There are two inequivalent C sites. In the first C site, C(1) is bonded to four equivalent Ho(1) and two equivalent Mo(1) atoms to form CHo4Mo2 octahedra that share corners with twelve equivalent C(2)Ho3Mo3 octahedra, edges with two equivalent C(1)Ho4Mo2 octahedra, and faces with two equivalent C(2)Ho3Mo3 octahedra. The corner-sharing octahedral tilt angles range from 43-57°. In the second C site, C(2) is bonded to three equivalent Ho(1) and three equivalent Mo(1) atoms to form CHo3Mo3 octahedra that share corners with six equivalent C(1)Ho4Mo2 octahedra, edges with six equivalent C(2)Ho3Mo3 octahedra, and  a faceface with one C(1)Ho4Mo2 octahedra. The corner-sharing octahedral tilt angles range from 43-57°.