ErCu3Ga2 crystallizes in the orthorhombic Cmmm space group. Er(1) is bonded in a 18-coordinate geometry to four equivalent Cu(2), six equivalent Cu(1), and eight equivalent Ga(1) atoms. There are two inequivalent Cu sites. In the first Cu site, Cu(2) is bonded to four equivalent Er(1), four equivalent Cu(1), and four equivalent Ga(1) atoms to form distorted CuEr4Ga4Cu4 cuboctahedra that share corners with eight equivalent Cu(2)Er4Ga4Cu4 cuboctahedra, corners with eight equivalent Ga(1)Er4Ga2Cu6 cuboctahedra, edges with two equivalent Cu(2)Er4Ga4Cu4 cuboctahedra, edges with eight equivalent Ga(1)Er4Ga2Cu6 cuboctahedra, faces with two equivalent Cu(2)Er4Ga4Cu4 cuboctahedra, and faces with eight equivalent Ga(1)Er4Ga2Cu6 cuboctahedra. In the second Cu site, Cu(1) is bonded in a 9-coordinate geometry to three equivalent Er(1), two equivalent Cu(2), and four equivalent Ga(1) atoms. Ga(1) is bonded to four equivalent Er(1), two equivalent Cu(2), four equivalent Cu(1), and two equivalent Ga(1) atoms to form distorted GaEr4Ga2Cu6 cuboctahedra that share corners with four equivalent Cu(2)Er4Ga4Cu4 cuboctahedra, corners with twelve equivalent Ga(1)Er4Ga2Cu6 cuboctahedra, edges with four equivalent Cu(2)Er4Ga4Cu4 cuboctahedra, edges with six equivalent Ga(1)Er4Ga2Cu6 cuboctahedra, faces with four equivalent Cu(2)Er4Ga4Cu4 cuboctahedra, and faces with six equivalent Ga(1)Er4Ga2Cu6 cuboctahedra.
ErCu3Ga2 crystallizes in the orthorhombic Cmmm space group. Er(1) is bonded in a 18-coordinate geometry to four equivalent Cu(2), six equivalent Cu(1), and eight equivalent Ga(1) atoms. All Er(1)-Cu(2) bond lengths are 3.28 Å. There are two shorter (2.93 Å) and four longer (2.94 Å) Er(1)-Cu(1) bond lengths. All Er(1)-Ga(1) bond lengths are 3.24 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(2) is bonded to four equivalent Er(1), four equivalent Cu(1), and four equivalent Ga(1) atoms to form distorted CuEr4Ga4Cu4 cuboctahedra that share corners with eight equivalent Cu(2)Er4Ga4Cu4 cuboctahedra, corners with eight equivalent Ga(1)Er4Ga2Cu6 cuboctahedra, edges with two equivalent Cu(2)Er4Ga4Cu4 cuboctahedra, edges with eight equivalent Ga(1)Er4Ga2Cu6 cuboctahedra, faces with two equivalent Cu(2)Er4Ga4Cu4 cuboctahedra, and faces with eight equivalent Ga(1)Er4Ga2Cu6 cuboctahedra. All Cu(2)-Cu(1) bond lengths are 2.47 Å. All Cu(2)-Ga(1) bond lengths are 2.52 Å. In the second Cu site, Cu(1) is bonded in a 9-coordinate geometry to three equivalent Er(1), two equivalent Cu(2), and four equivalent Ga(1) atoms. All Cu(1)-Ga(1) bond lengths are 2.53 Å. Ga(1) is bonded to four equivalent Er(1), two equivalent Cu(2), four equivalent Cu(1), and two equivalent Ga(1) atoms to form distorted GaEr4Ga2Cu6 cuboctahedra that share corners with four equivalent Cu(2)Er4Ga4Cu4 cuboctahedra, corners with twelve equivalent Ga(1)Er4Ga2Cu6 cuboctahedra, edges with four equivalent Cu(2)Er4Ga4Cu4 cuboctahedra, edges with six equivalent Ga(1)Er4Ga2Cu6 cuboctahedra, faces with four equivalent Cu(2)Er4Ga4Cu4 cuboctahedra, and faces with six equivalent Ga(1)Er4Ga2Cu6 cuboctahedra. Both Ga(1)-Ga(1) bond lengths are 2.58 Å.