Y3(CuSi)4 crystallizes in the orthorhombic Immm space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded in a 12-coordinate geometry to six equivalent Cu(1), two equivalent Si(1), and four equivalent Si(2) atoms. In the second Y site, Y(2) is bonded to two equivalent Si(1) and four equivalent Si(2) atoms to form distorted edge-sharing YSi6 octahedra. Cu(1) is bonded in a 8-coordinate geometry to three equivalent Y(1), 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 Y(2), two equivalent Y(1), and six equivalent Cu(1) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Y(2), four equivalent Y(1), two equivalent Cu(1), and one Si(2) atom.
Y3(CuSi)4 crystallizes in the orthorhombic Immm space group. There are two inequivalent Y sites. In the first Y site, Y(1) 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 (2.95 Å) and two longer (3.04 Å) Y(1)-Cu(1) bond lengths. Both Y(1)-Si(1) bond lengths are 2.97 Å. All Y(1)-Si(2) bond lengths are 2.98 Å. In the second Y site, Y(2) is bonded to two equivalent Si(1) and four equivalent Si(2) atoms to form distorted edge-sharing YSi6 octahedra. Both Y(2)-Si(1) bond lengths are 2.96 Å. All Y(2)-Si(2) bond lengths are 2.93 Å. Cu(1) is bonded in a 8-coordinate geometry to three equivalent Y(1), one Cu(1), one Si(2), and three equivalent Si(1) atoms. The Cu(1)-Cu(1) bond length is 2.49 Å. The Cu(1)-Si(2) bond length is 2.46 Å. There are two shorter (2.50 Å) and one longer (2.57 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 Y(2), two equivalent Y(1), and six equivalent Cu(1) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Y(2), four equivalent Y(1), two equivalent Cu(1), and one Si(2) atom. The Si(2)-Si(2) bond length is 2.41 Å.