YbCu5S4 crystallizes in the monoclinic C2/m space group. Yb(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form YbS6 octahedra that share corners with two equivalent Cu(2)S4 tetrahedra, corners with ten equivalent Cu(3)S4 tetrahedra, edges with two equivalent Yb(1)S6 octahedra, edges with four equivalent Cu(1)S6 octahedra, edges with two equivalent Cu(3)S4 tetrahedra, and edges with four equivalent Cu(2)S4 tetrahedra. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent S(1) and four equivalent S(2) atoms to form CuS6 octahedra that share corners with two equivalent Cu(3)S4 tetrahedra, corners with ten equivalent Cu(2)S4 tetrahedra, edges with two equivalent Cu(1)S6 octahedra, edges with four equivalent Yb(1)S6 octahedra, edges with two equivalent Cu(2)S4 tetrahedra, and edges with four equivalent Cu(3)S4 tetrahedra. In the second Cu site, Cu(2) is bonded to one S(1) and three equivalent S(2) atoms to form CuS4 tetrahedra that share  a cornercorner with one Yb(1)S6 octahedra, corners with five equivalent Cu(1)S6 octahedra, corners with two equivalent Cu(2)S4 tetrahedra, corners with four equivalent Cu(3)S4 tetrahedra,  an edgeedge with one Cu(1)S6 octahedra, edges with two equivalent Yb(1)S6 octahedra,  an edgeedge with one Cu(3)S4 tetrahedra, and edges with two equivalent Cu(2)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 16-56°. In the third Cu site, Cu(3) is bonded to one S(2) and three equivalent S(1) atoms to form CuS4 tetrahedra that share  a cornercorner with one Cu(1)S6 octahedra, corners with five equivalent Yb(1)S6 octahedra, corners with two equivalent Cu(3)S4 tetrahedra, corners with four equivalent Cu(2)S4 tetrahedra,  an edgeedge with one Yb(1)S6 octahedra, edges with two equivalent Cu(1)S6 octahedra,  an edgeedge with one Cu(2)S4 tetrahedra, and edges with two equivalent Cu(3)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 14-55°. There are two inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Yb(1), one Cu(1), one Cu(2), and three equivalent Cu(3) atoms to form distorted SYb2Cu5 pentagonal bipyramids that share corners with three equivalent S(1)Yb2Cu5 pentagonal bipyramids, edges with five equivalent S(1)Yb2Cu5 pentagonal bipyramids, and edges with seven equivalent S(2)YbCu6 pentagonal bipyramids. In the second S site, S(2) is bonded to one Yb(1), one Cu(3), two equivalent Cu(1), and three equivalent Cu(2) atoms to form distorted SYbCu6 pentagonal bipyramids that share corners with three equivalent S(2)YbCu6 pentagonal bipyramids, edges with five equivalent S(2)YbCu6 pentagonal bipyramids, and edges with seven equivalent S(1)Yb2Cu5 pentagonal bipyramids.
YbCu5S4 crystallizes in the monoclinic C2/m space group. Yb(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form YbS6 octahedra that share corners with two equivalent Cu(2)S4 tetrahedra, corners with ten equivalent Cu(3)S4 tetrahedra, edges with two equivalent Yb(1)S6 octahedra, edges with four equivalent Cu(1)S6 octahedra, edges with two equivalent Cu(3)S4 tetrahedra, and edges with four equivalent Cu(2)S4 tetrahedra. Both Yb(1)-S(2) bond lengths are 2.74 Å. All Yb(1)-S(1) bond lengths are 2.72 Å. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent S(1) and four equivalent S(2) atoms to form CuS6 octahedra that share corners with two equivalent Cu(3)S4 tetrahedra, corners with ten equivalent Cu(2)S4 tetrahedra, edges with two equivalent Cu(1)S6 octahedra, edges with four equivalent Yb(1)S6 octahedra, edges with two equivalent Cu(2)S4 tetrahedra, and edges with four equivalent Cu(3)S4 tetrahedra. Both Cu(1)-S(1) bond lengths are 2.68 Å. All Cu(1)-S(2) bond lengths are 2.67 Å. In the second Cu site, Cu(2) is bonded to one S(1) and three equivalent S(2) atoms to form CuS4 tetrahedra that share  a cornercorner with one Yb(1)S6 octahedra, corners with five equivalent Cu(1)S6 octahedra, corners with two equivalent Cu(2)S4 tetrahedra, corners with four equivalent Cu(3)S4 tetrahedra,  an edgeedge with one Cu(1)S6 octahedra, edges with two equivalent Yb(1)S6 octahedra,  an edgeedge with one Cu(3)S4 tetrahedra, and edges with two equivalent Cu(2)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 16-56°. The Cu(2)-S(1) bond length is 2.37 Å. There are two shorter (2.36 Å) and one longer (2.42 Å) Cu(2)-S(2) bond length. In the third Cu site, Cu(3) is bonded to one S(2) and three equivalent S(1) atoms to form CuS4 tetrahedra that share  a cornercorner with one Cu(1)S6 octahedra, corners with five equivalent Yb(1)S6 octahedra, corners with two equivalent Cu(3)S4 tetrahedra, corners with four equivalent Cu(2)S4 tetrahedra,  an edgeedge with one Yb(1)S6 octahedra, edges with two equivalent Cu(1)S6 octahedra,  an edgeedge with one Cu(2)S4 tetrahedra, and edges with two equivalent Cu(3)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 14-55°. The Cu(3)-S(2) bond length is 2.29 Å. There are two shorter (2.30 Å) and one longer (2.41 Å) Cu(3)-S(1) bond length. There are two inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Yb(1), one Cu(1), one Cu(2), and three equivalent Cu(3) atoms to form distorted SYb2Cu5 pentagonal bipyramids that share corners with three equivalent S(1)Yb2Cu5 pentagonal bipyramids, edges with five equivalent S(1)Yb2Cu5 pentagonal bipyramids, and edges with seven equivalent S(2)YbCu6 pentagonal bipyramids. In the second S site, S(2) is bonded to one Yb(1), one Cu(3), two equivalent Cu(1), and three equivalent Cu(2) atoms to form distorted SYbCu6 pentagonal bipyramids that share corners with three equivalent S(2)YbCu6 pentagonal bipyramids, edges with five equivalent S(2)YbCu6 pentagonal bipyramids, and edges with seven equivalent S(1)Yb2Cu5 pentagonal bipyramids.