MgHo2S4 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to two equivalent S(4) and three equivalent S(1) atoms to form MgS5 square pyramids that share corners with two equivalent Ho(1)S6 octahedra, corners with two equivalent Ho(2)S6 octahedra,  an edgeedge with one Ho(1)S6 octahedra, edges with three equivalent Ho(2)S6 octahedra, and edges with four equivalent Mg(1)S5 square pyramids. The corner-sharing octahedral tilt angles range from 6-11°. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded to one S(3), two equivalent S(4), and three equivalent S(2) atoms to form HoS6 octahedra that share corners with three equivalent Ho(2)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Ho(2)S6 octahedra, edges with four equivalent Ho(1)S6 octahedra, and  an edgeedge with one Mg(1)S5 square pyramid. The corner-sharing octahedral tilt angles range from 53-59°. In the second Ho site, Ho(2) is bonded to one S(2), one S(4), two equivalent S(1), and two equivalent S(3) atoms to form HoS6 octahedra that share corners with three equivalent Ho(1)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Ho(1)S6 octahedra, edges with two equivalent Ho(2)S6 octahedra, and edges with three equivalent Mg(1)S5 square pyramids. The corner-sharing octahedral tilt angles range from 53-59°. There are four inequivalent S sites. In the first S site, S(1) is bonded to three equivalent Mg(1) and two equivalent Ho(2) atoms to form SHo2Mg3 square pyramids that share corners with two equivalent S(4)Ho3Mg2 square pyramids, edges with three equivalent S(4)Ho3Mg2 square pyramids, and edges with four equivalent S(1)Ho2Mg3 square pyramids. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Ho(2) and three equivalent Ho(1) atoms. In the third S site, S(3) is bonded in a distorted T-shaped geometry to one Ho(1) and two equivalent Ho(2) atoms. In the fourth S site, S(4) is bonded to two equivalent Mg(1), one Ho(2), and two equivalent Ho(1) atoms to form SHo3Mg2 square pyramids that share corners with two equivalent S(1)Ho2Mg3 square pyramids, edges with two equivalent S(4)Ho3Mg2 square pyramids, and edges with three equivalent S(1)Ho2Mg3 square pyramids.
MgHo2S4 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to two equivalent S(4) and three equivalent S(1) atoms to form MgS5 square pyramids that share corners with two equivalent Ho(1)S6 octahedra, corners with two equivalent Ho(2)S6 octahedra,  an edgeedge with one Ho(1)S6 octahedra, edges with three equivalent Ho(2)S6 octahedra, and edges with four equivalent Mg(1)S5 square pyramids. The corner-sharing octahedral tilt angles range from 6-11°. Both Mg(1)-S(4) bond lengths are 2.68 Å. There is one shorter (2.61 Å) and two longer (2.62 Å) Mg(1)-S(1) bond lengths. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded to one S(3), two equivalent S(4), and three equivalent S(2) atoms to form HoS6 octahedra that share corners with three equivalent Ho(2)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Ho(2)S6 octahedra, edges with four equivalent Ho(1)S6 octahedra, and  an edgeedge with one Mg(1)S5 square pyramid. The corner-sharing octahedral tilt angles range from 53-59°. The Ho(1)-S(3) bond length is 2.70 Å. Both Ho(1)-S(4) bond lengths are 2.75 Å. There are two shorter (2.69 Å) and one longer (2.80 Å) Ho(1)-S(2) bond length. In the second Ho site, Ho(2) is bonded to one S(2), one S(4), two equivalent S(1), and two equivalent S(3) atoms to form HoS6 octahedra that share corners with three equivalent Ho(1)S6 octahedra, corners with two equivalent Mg(1)S5 square pyramids, edges with two equivalent Ho(1)S6 octahedra, edges with two equivalent Ho(2)S6 octahedra, and edges with three equivalent Mg(1)S5 square pyramids. The corner-sharing octahedral tilt angles range from 53-59°. The Ho(2)-S(2) bond length is 2.75 Å. The Ho(2)-S(4) bond length is 2.79 Å. Both Ho(2)-S(1) bond lengths are 2.77 Å. Both Ho(2)-S(3) bond lengths are 2.66 Å. There are four inequivalent S sites. In the first S site, S(1) is bonded to three equivalent Mg(1) and two equivalent Ho(2) atoms to form SHo2Mg3 square pyramids that share corners with two equivalent S(4)Ho3Mg2 square pyramids, edges with three equivalent S(4)Ho3Mg2 square pyramids, and edges with four equivalent S(1)Ho2Mg3 square pyramids. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Ho(2) and three equivalent Ho(1) atoms. In the third S site, S(3) is bonded in a distorted T-shaped geometry to one Ho(1) and two equivalent Ho(2) atoms. In the fourth S site, S(4) is bonded to two equivalent Mg(1), one Ho(2), and two equivalent Ho(1) atoms to form SHo3Mg2 square pyramids that share corners with two equivalent S(1)Ho2Mg3 square pyramids, edges with two equivalent S(4)Ho3Mg2 square pyramids, and edges with three equivalent S(1)Ho2Mg3 square pyramids.