Lu3(CuSi)4 crystallizes in the orthorhombic Immm space group. There are two inequivalent Lu sites. In the first Lu site, Lu(1) is bonded to two equivalent Si(1) and four equivalent Si(2) atoms to form distorted edge-sharing LuSi6 octahedra. In the second Lu site, Lu(2) is bonded in a 12-coordinate geometry to six equivalent Cu(1), two equivalent Si(1), and four equivalent Si(2) atoms. Cu(1) is bonded in a 8-coordinate geometry to three equivalent Lu(2), one Cu(1), one Si(2), and three equivalent Si(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Lu(1), two equivalent Lu(2), and six equivalent Cu(1) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Lu(1), four equivalent Lu(2), two equivalent Cu(1), and one Si(2) atom.
Lu3(CuSi)4 crystallizes in the orthorhombic Immm space group. There are two inequivalent Lu sites. In the first Lu site, Lu(1) is bonded to two equivalent Si(1) and four equivalent Si(2) atoms to form distorted edge-sharing LuSi6 octahedra. Both Lu(1)-Si(1) bond lengths are 2.92 Å. All Lu(1)-Si(2) bond lengths are 2.87 Å. In the second Lu site, Lu(2) is bonded in a 12-coordinate geometry to six equivalent Cu(1), two equivalent Si(1), and four equivalent Si(2) atoms. There are four shorter (2.91 Å) and two longer (2.99 Å) Lu(2)-Cu(1) bond lengths. Both Lu(2)-Si(1) bond lengths are 2.92 Å. All Lu(2)-Si(2) bond lengths are 2.92 Å. Cu(1) is bonded in a 8-coordinate geometry to three equivalent Lu(2), one Cu(1), one Si(2), and three equivalent Si(1) atoms. The Cu(1)-Cu(1) bond length is 2.47 Å. The Cu(1)-Si(2) bond length is 2.42 Å. There are two shorter (2.47 Å) and one longer (2.51 Å) Cu(1)-Si(1) bond length. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Lu(1), two equivalent Lu(2), and six equivalent Cu(1) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Lu(1), four equivalent Lu(2), two equivalent Cu(1), and one Si(2) atom. The Si(2)-Si(2) bond length is 2.41 Å.