CsHoCoSe3 crystallizes in the orthorhombic Cmcm space group. Cs(1) is bonded in a 8-coordinate geometry to two equivalent Se(1) and six equivalent Se(2) atoms. Ho(1) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form HoSe6 octahedra that share corners with two equivalent Ho(1)Se6 octahedra, edges with two equivalent Ho(1)Se6 octahedra, and edges with four equivalent Co(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles are 35°. Co(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form CoSe4 tetrahedra that share corners with two equivalent Co(1)Se4 tetrahedra and edges with four equivalent Ho(1)Se6 octahedra. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to two equivalent Cs(1), two equivalent Ho(1), and two equivalent Co(1) atoms. In the second Se site, Se(2) is bonded in a 6-coordinate geometry to three equivalent Cs(1), two equivalent Ho(1), and one Co(1) atom.
CsHoCoSe3 crystallizes in the orthorhombic Cmcm space group. Cs(1) is bonded in a 8-coordinate geometry to two equivalent Se(1) and six equivalent Se(2) atoms. Both Cs(1)-Se(1) bond lengths are 3.68 Å. There are four shorter (3.72 Å) and two longer (3.99 Å) Cs(1)-Se(2) bond lengths. Ho(1) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form HoSe6 octahedra that share corners with two equivalent Ho(1)Se6 octahedra, edges with two equivalent Ho(1)Se6 octahedra, and edges with four equivalent Co(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles are 35°. Both Ho(1)-Se(1) bond lengths are 2.85 Å. All Ho(1)-Se(2) bond lengths are 2.86 Å. Co(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form CoSe4 tetrahedra that share corners with two equivalent Co(1)Se4 tetrahedra and edges with four equivalent Ho(1)Se6 octahedra. Both Co(1)-Se(1) bond lengths are 2.49 Å. Both Co(1)-Se(2) bond lengths are 2.40 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to two equivalent Cs(1), two equivalent Ho(1), and two equivalent Co(1) atoms. In the second Se site, Se(2) is bonded in a 6-coordinate geometry to three equivalent Cs(1), two equivalent Ho(1), and one Co(1) atom.