KTbGeS4 crystallizes in the monoclinic P2_1 space group. K(1) is bonded in a 8-coordinate geometry to one S(3), two equivalent S(1), two equivalent S(4), and three equivalent S(2) atoms. Tb(1) is bonded to one S(2), two equivalent S(1), two equivalent S(3), and two equivalent S(4) atoms to form distorted TbS7 pentagonal bipyramids that share corners with two equivalent Tb(1)S7 pentagonal bipyramids,  a cornercorner with one Ge(1)S4 tetrahedra, edges with two equivalent Tb(1)S7 pentagonal bipyramids, and edges with three equivalent Ge(1)S4 tetrahedra. Ge(1) is bonded to one S(1), one S(2), one S(3), and one S(4) atom to form GeS4 tetrahedra that share  a cornercorner with one Tb(1)S7 pentagonal bipyramid and edges with three equivalent Tb(1)S7 pentagonal bipyramids. There are four inequivalent S sites. In the first S site, S(1) is bonded to two equivalent K(1), two equivalent Tb(1), and one Ge(1) atom to form distorted SK2Tb2Ge square pyramids that share corners with four equivalent S(1)K2Tb2Ge square pyramids, corners with five equivalent S(2)K3TbGe trigonal bipyramids, and edges with two equivalent S(2)K3TbGe trigonal bipyramids. In the second S site, S(2) is bonded to three equivalent K(1), one Tb(1), and one Ge(1) atom to form distorted SK3TbGe trigonal bipyramids that share corners with five equivalent S(1)K2Tb2Ge square pyramids, corners with two equivalent S(2)K3TbGe trigonal bipyramids, edges with two equivalent S(1)K2Tb2Ge square pyramids, and edges with two equivalent S(2)K3TbGe trigonal bipyramids. In the third S site, S(3) is bonded in a distorted see-saw-like geometry to one K(1), two equivalent Tb(1), and one Ge(1) atom. In the fourth S site, S(4) is bonded in a 5-coordinate geometry to two equivalent K(1), two equivalent Tb(1), and one Ge(1) atom.
KTbGeS4 crystallizes in the monoclinic P2_1 space group. K(1) is bonded in a 8-coordinate geometry to one S(3), two equivalent S(1), two equivalent S(4), and three equivalent S(2) atoms. The K(1)-S(3) bond length is 3.25 Å. There is one shorter (3.45 Å) and one longer (3.50 Å) K(1)-S(1) bond length. There is one shorter (3.42 Å) and one longer (3.65 Å) K(1)-S(4) bond length. There are a spread of K(1)-S(2) bond distances ranging from 3.25-3.68 Å. Tb(1) is bonded to one S(2), two equivalent S(1), two equivalent S(3), and two equivalent S(4) atoms to form distorted TbS7 pentagonal bipyramids that share corners with two equivalent Tb(1)S7 pentagonal bipyramids,  a cornercorner with one Ge(1)S4 tetrahedra, edges with two equivalent Tb(1)S7 pentagonal bipyramids, and edges with three equivalent Ge(1)S4 tetrahedra. The Tb(1)-S(2) bond length is 2.81 Å. There is one shorter (2.89 Å) and one longer (2.90 Å) Tb(1)-S(1) bond length. There is one shorter (2.83 Å) and one longer (2.95 Å) Tb(1)-S(3) bond length. There is one shorter (2.83 Å) and one longer (2.85 Å) Tb(1)-S(4) bond length. Ge(1) is bonded to one S(1), one S(2), one S(3), and one S(4) atom to form GeS4 tetrahedra that share  a cornercorner with one Tb(1)S7 pentagonal bipyramid and edges with three equivalent Tb(1)S7 pentagonal bipyramids. The Ge(1)-S(1) bond length is 2.24 Å. The Ge(1)-S(2) bond length is 2.20 Å. The Ge(1)-S(3) bond length is 2.23 Å. The Ge(1)-S(4) bond length is 2.24 Å. There are four inequivalent S sites. In the first S site, S(1) is bonded to two equivalent K(1), two equivalent Tb(1), and one Ge(1) atom to form distorted SK2Tb2Ge square pyramids that share corners with four equivalent S(1)K2Tb2Ge square pyramids, corners with five equivalent S(2)K3TbGe trigonal bipyramids, and edges with two equivalent S(2)K3TbGe trigonal bipyramids. In the second S site, S(2) is bonded to three equivalent K(1), one Tb(1), and one Ge(1) atom to form distorted SK3TbGe trigonal bipyramids that share corners with five equivalent S(1)K2Tb2Ge square pyramids, corners with two equivalent S(2)K3TbGe trigonal bipyramids, edges with two equivalent S(1)K2Tb2Ge square pyramids, and edges with two equivalent S(2)K3TbGe trigonal bipyramids. In the third S site, S(3) is bonded in a distorted see-saw-like geometry to one K(1), two equivalent Tb(1), and one Ge(1) atom. In the fourth S site, S(4) is bonded in a 5-coordinate geometry to two equivalent K(1), two equivalent Tb(1), and one Ge(1) atom.