MgTm2S4 is Spinel-like structured and crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to one S(2), one S(3), and two equivalent S(1) atoms to form MgS4 tetrahedra that share corners with two equivalent Tm(1)S6 octahedra, corners with four equivalent Tm(2)S6 octahedra,  an edgeedge with one Tm(2)S6 octahedra, and edges with two equivalent Tm(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 59-67°. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded to two equivalent S(1), two equivalent S(2), and two equivalent S(3) atoms to form TmS6 octahedra that share corners with four equivalent Tm(2)S6 octahedra, corners with two equivalent Mg(1)S4 tetrahedra, edges with two equivalent Tm(1)S6 octahedra, edges with two equivalent Tm(2)S6 octahedra, and edges with two equivalent Mg(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-54°. In the second Tm site, Tm(2) is bonded to one S(2), one S(3), and four equivalent S(1) atoms to form TmS6 octahedra that share corners with four equivalent Tm(1)S6 octahedra, corners with four equivalent Tm(2)S6 octahedra, corners with four equivalent Mg(1)S4 tetrahedra, edges with two equivalent Tm(1)S6 octahedra, and  an edgeedge with one Mg(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-54°. There are three inequivalent S sites. In the first S site, S(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Tm(1), and two equivalent Tm(2) atoms. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Tm(2), and two equivalent Tm(1) atoms. In the third S site, S(3) is bonded to one Mg(1), one Tm(2), and two equivalent Tm(1) atoms to form distorted corner-sharing STm3Mg trigonal pyramids.
MgTm2S4 is Spinel-like structured and crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to one S(2), one S(3), and two equivalent S(1) atoms to form MgS4 tetrahedra that share corners with two equivalent Tm(1)S6 octahedra, corners with four equivalent Tm(2)S6 octahedra,  an edgeedge with one Tm(2)S6 octahedra, and edges with two equivalent Tm(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 59-67°. The Mg(1)-S(2) bond length is 2.47 Å. The Mg(1)-S(3) bond length is 2.39 Å. Both Mg(1)-S(1) bond lengths are 2.46 Å. There are two inequivalent Tm sites. In the first Tm site, Tm(1) is bonded to two equivalent S(1), two equivalent S(2), and two equivalent S(3) atoms to form TmS6 octahedra that share corners with four equivalent Tm(2)S6 octahedra, corners with two equivalent Mg(1)S4 tetrahedra, edges with two equivalent Tm(1)S6 octahedra, edges with two equivalent Tm(2)S6 octahedra, and edges with two equivalent Mg(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-54°. Both Tm(1)-S(1) bond lengths are 2.74 Å. Both Tm(1)-S(2) bond lengths are 2.71 Å. Both Tm(1)-S(3) bond lengths are 2.66 Å. In the second Tm site, Tm(2) is bonded to one S(2), one S(3), and four equivalent S(1) atoms to form TmS6 octahedra that share corners with four equivalent Tm(1)S6 octahedra, corners with four equivalent Tm(2)S6 octahedra, corners with four equivalent Mg(1)S4 tetrahedra, edges with two equivalent Tm(1)S6 octahedra, and  an edgeedge with one Mg(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-54°. The Tm(2)-S(2) bond length is 2.69 Å. The Tm(2)-S(3) bond length is 2.70 Å. There are two shorter (2.76 Å) and two longer (2.77 Å) Tm(2)-S(1) bond lengths. There are three inequivalent S sites. In the first S site, S(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Tm(1), and two equivalent Tm(2) atoms. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Tm(2), and two equivalent Tm(1) atoms. In the third S site, S(3) is bonded to one Mg(1), one Tm(2), and two equivalent Tm(1) atoms to form distorted corner-sharing STm3Mg trigonal pyramids.