UY(CuSi)4 crystallizes in the tetragonal P4/mmm space group. U(1) is bonded in a 16-coordinate geometry to eight equivalent Cu(1) and eight equivalent Si(1) atoms. Y(1) is bonded in a 16-coordinate geometry to eight equivalent Cu(1) and eight equivalent Si(2) atoms. Cu(1) is bonded to two equivalent U(1), two equivalent Y(1), four equivalent Cu(1), two equivalent Si(1), and two equivalent Si(2) atoms to form a mixture of distorted face, corner, and edge-sharing CuY2U2Cu4Si4 cuboctahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to four equivalent U(1), four equivalent Cu(1), and one Si(1) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to four equivalent Y(1), four equivalent Cu(1), and one Si(2) atom.
UY(CuSi)4 crystallizes in the tetragonal P4/mmm space group. U(1) is bonded in a 16-coordinate geometry to eight equivalent Cu(1) and eight equivalent Si(1) atoms. All U(1)-Cu(1) bond lengths are 3.20 Å. All U(1)-Si(1) bond lengths are 3.04 Å. Y(1) is bonded in a 16-coordinate geometry to eight equivalent Cu(1) and eight equivalent Si(2) atoms. All Y(1)-Cu(1) bond lengths are 3.18 Å. All Y(1)-Si(2) bond lengths are 3.05 Å. Cu(1) is bonded to two equivalent U(1), two equivalent Y(1), four equivalent Cu(1), two equivalent Si(1), and two equivalent Si(2) atoms to form a mixture of distorted face, corner, and edge-sharing CuY2U2Cu4Si4 cuboctahedra. All Cu(1)-Cu(1) bond lengths are 2.81 Å. Both Cu(1)-Si(1) bond lengths are 2.40 Å. Both Cu(1)-Si(2) bond lengths are 2.37 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to four equivalent U(1), four equivalent Cu(1), and one Si(1) atom. The Si(1)-Si(1) bond length is 2.32 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to four equivalent Y(1), four equivalent Cu(1), and one Si(2) atom. The Si(2)-Si(2) bond length is 2.38 Å.