TlIn5Se7 crystallizes in the monoclinic P2_1/m space group. Tl(1) is bonded in a 4-coordinate geometry to two equivalent Se(6) and two equivalent Se(7) atoms. There are five inequivalent In sites. In the first In site, In(1) is bonded to one Se(2), two equivalent Se(3), and three equivalent Se(7) atoms to form a mixture of edge and corner-sharing InSe6 octahedra. The corner-sharing octahedral tilt angles are 1°. In the second In site, In(2) is bonded in a 3-coordinate geometry to one Se(5) and two equivalent Se(1) atoms. In the third In site, In(3) is bonded in a 3-coordinate geometry to one Se(4) and two equivalent Se(6) atoms. In the fourth In site, In(4) is bonded to one Se(6), two equivalent Se(4), and three equivalent Se(5) atoms to form edge-sharing InSe6 octahedra. In the fifth In site, In(5) is bonded to one Se(1), two equivalent Se(2), and three equivalent Se(3) atoms to form a mixture of edge and corner-sharing InSe6 octahedra. The corner-sharing octahedral tilt angles are 1°. There are seven inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one In(5) and two equivalent In(2) atoms. In the second Se site, Se(2) is bonded in a distorted T-shaped geometry to one In(1) and two equivalent In(5) atoms. In the third Se site, Se(3) is bonded to two equivalent In(1) and three equivalent In(5) atoms to form SeIn5 square pyramids that share corners with four equivalent Se(7)Tl2In3 trigonal bipyramids, edges with four equivalent Se(3)In5 square pyramids, and  an edgeedge with one Se(7)Tl2In3 trigonal bipyramid. In the fourth Se site, Se(4) is bonded in a distorted T-shaped geometry to one In(3) and two equivalent In(4) atoms. In the fifth Se site, Se(5) is bonded in a rectangular see-saw-like geometry to one In(2) and three equivalent In(4) atoms. In the sixth Se site, Se(6) is bonded to two equivalent Tl(1), one In(4), and two equivalent In(3) atoms to form a mixture of distorted edge and corner-sharing SeTl2In3 square pyramids. In the seventh Se site, Se(7) is bonded to two equivalent Tl(1) and three equivalent In(1) atoms to form distorted SeTl2In3 trigonal bipyramids that share corners with two equivalent Se(6)Tl2In3 square pyramids, corners with four equivalent Se(3)In5 square pyramids,  an edgeedge with one Se(3)In5 square pyramid,  an edgeedge with one Se(6)Tl2In3 square pyramid, and edges with four equivalent Se(7)Tl2In3 trigonal bipyramids.
TlIn5Se7 crystallizes in the monoclinic P2_1/m space group. Tl(1) is bonded in a 4-coordinate geometry to two equivalent Se(6) and two equivalent Se(7) atoms. Both Tl(1)-Se(6) bond lengths are 3.30 Å. Both Tl(1)-Se(7) bond lengths are 3.25 Å. There are five inequivalent In sites. In the first In site, In(1) is bonded to one Se(2), two equivalent Se(3), and three equivalent Se(7) atoms to form a mixture of edge and corner-sharing InSe6 octahedra. The corner-sharing octahedral tilt angles are 1°. The In(1)-Se(2) bond length is 2.70 Å. Both In(1)-Se(3) bond lengths are 2.97 Å. There is one shorter (2.69 Å) and two longer (2.78 Å) In(1)-Se(7) bond lengths. In the second In site, In(2) is bonded in a 3-coordinate geometry to one Se(5) and two equivalent Se(1) atoms. The In(2)-Se(5) bond length is 2.79 Å. Both In(2)-Se(1) bond lengths are 2.71 Å. In the third In site, In(3) is bonded in a 3-coordinate geometry to one Se(4) and two equivalent Se(6) atoms. The In(3)-Se(4) bond length is 2.68 Å. Both In(3)-Se(6) bond lengths are 2.73 Å. In the fourth In site, In(4) is bonded to one Se(6), two equivalent Se(4), and three equivalent Se(5) atoms to form edge-sharing InSe6 octahedra. The In(4)-Se(6) bond length is 2.77 Å. Both In(4)-Se(4) bond lengths are 2.80 Å. There is one shorter (2.81 Å) and two longer (2.86 Å) In(4)-Se(5) bond lengths. In the fifth In site, In(5) is bonded to one Se(1), two equivalent Se(2), and three equivalent Se(3) atoms to form a mixture of edge and corner-sharing InSe6 octahedra. The corner-sharing octahedral tilt angles are 1°. The In(5)-Se(1) bond length is 2.80 Å. Both In(5)-Se(2) bond lengths are 2.73 Å. There is one shorter (2.75 Å) and two longer (2.96 Å) In(5)-Se(3) bond lengths. There are seven inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one In(5) and two equivalent In(2) atoms. In the second Se site, Se(2) is bonded in a distorted T-shaped geometry to one In(1) and two equivalent In(5) atoms. In the third Se site, Se(3) is bonded to two equivalent In(1) and three equivalent In(5) atoms to form SeIn5 square pyramids that share corners with four equivalent Se(7)Tl2In3 trigonal bipyramids, edges with four equivalent Se(3)In5 square pyramids, and  an edgeedge with one Se(7)Tl2In3 trigonal bipyramid. In the fourth Se site, Se(4) is bonded in a distorted T-shaped geometry to one In(3) and two equivalent In(4) atoms. In the fifth Se site, Se(5) is bonded in a rectangular see-saw-like geometry to one In(2) and three equivalent In(4) atoms. In the sixth Se site, Se(6) is bonded to two equivalent Tl(1), one In(4), and two equivalent In(3) atoms to form a mixture of distorted edge and corner-sharing SeTl2In3 square pyramids. In the seventh Se site, Se(7) is bonded to two equivalent Tl(1) and three equivalent In(1) atoms to form distorted SeTl2In3 trigonal bipyramids that share corners with two equivalent Se(6)Tl2In3 square pyramids, corners with four equivalent Se(3)In5 square pyramids,  an edgeedge with one Se(3)In5 square pyramid,  an edgeedge with one Se(6)Tl2In3 square pyramid, and edges with four equivalent Se(7)Tl2In3 trigonal bipyramids.