YbCuAl2 crystallizes in the trigonal R-3m space group. There are two inequivalent Yb sites. In the first Yb site, Yb(1) is bonded in a 18-coordinate geometry to six equivalent Cu(1) and twelve equivalent Al(1) atoms. In the second Yb site, Yb(2) is bonded in a 12-coordinate geometry to three equivalent Cu(2) and nine equivalent Al(1) atoms. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 9-coordinate geometry to three equivalent Yb(1) and six equivalent Al(1) atoms. In the second Cu site, Cu(2) is bonded to six equivalent Yb(2) and six equivalent Al(1) atoms to form CuYb6Al6 cuboctahedra that share corners with twelve equivalent Al(1)Yb5Al4Cu3 cuboctahedra, edges with six equivalent Cu(2)Yb6Al6 cuboctahedra, and faces with eighteen equivalent Al(1)Yb5Al4Cu3 cuboctahedra. Al(1) is bonded to two equivalent Yb(1), three equivalent Yb(2), one Cu(2), two equivalent Cu(1), and four equivalent Al(1) atoms to form distorted AlYb5Al4Cu3 cuboctahedra that share corners with two equivalent Cu(2)Yb6Al6 cuboctahedra, corners with fifteen equivalent Al(1)Yb5Al4Cu3 cuboctahedra, edges with eight equivalent Al(1)Yb5Al4Cu3 cuboctahedra, faces with three equivalent Cu(2)Yb6Al6 cuboctahedra, and faces with eleven equivalent Al(1)Yb5Al4Cu3 cuboctahedra.
YbCuAl2 crystallizes in the trigonal R-3m space group. There are two inequivalent Yb sites. In the first Yb site, Yb(1) is bonded in a 18-coordinate geometry to six equivalent Cu(1) and twelve equivalent Al(1) atoms. All Yb(1)-Cu(1) bond lengths are 3.13 Å. All Yb(1)-Al(1) bond lengths are 3.37 Å. In the second Yb site, Yb(2) is bonded in a 12-coordinate geometry to three equivalent Cu(2) and nine equivalent Al(1) atoms. All Yb(2)-Cu(2) bond lengths are 3.17 Å. There are three shorter (3.17 Å) and six longer (3.18 Å) Yb(2)-Al(1) bond lengths. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 9-coordinate geometry to three equivalent Yb(1) and six equivalent Al(1) atoms. There are three shorter (2.52 Å) and three longer (2.57 Å) Cu(1)-Al(1) bond lengths. In the second Cu site, Cu(2) is bonded to six equivalent Yb(2) and six equivalent Al(1) atoms to form CuYb6Al6 cuboctahedra that share corners with twelve equivalent Al(1)Yb5Al4Cu3 cuboctahedra, edges with six equivalent Cu(2)Yb6Al6 cuboctahedra, and faces with eighteen equivalent Al(1)Yb5Al4Cu3 cuboctahedra. All Cu(2)-Al(1) bond lengths are 2.72 Å. Al(1) is bonded to two equivalent Yb(1), three equivalent Yb(2), one Cu(2), two equivalent Cu(1), and four equivalent Al(1) atoms to form distorted AlYb5Al4Cu3 cuboctahedra that share corners with two equivalent Cu(2)Yb6Al6 cuboctahedra, corners with fifteen equivalent Al(1)Yb5Al4Cu3 cuboctahedra, edges with eight equivalent Al(1)Yb5Al4Cu3 cuboctahedra, faces with three equivalent Cu(2)Yb6Al6 cuboctahedra, and faces with eleven equivalent Al(1)Yb5Al4Cu3 cuboctahedra. There are two shorter (2.70 Å) and two longer (2.71 Å) Al(1)-Al(1) bond lengths.