UNiGa5 crystallizes in the tetragonal P4/mmm space group. U(1) is bonded to four equivalent Ga(2) and eight equivalent Ga(1) atoms to form UGa12 cuboctahedra that share corners with four equivalent U(1)Ga12 cuboctahedra, faces with four equivalent U(1)Ga12 cuboctahedra, and faces with four equivalent Ga(2)U4Ga8 cuboctahedra. Ni(1) is bonded in a body-centered cubic geometry to eight equivalent Ga(1) atoms. There are two inequivalent Ga sites. In the first Ga site, Ga(1) is bonded in a 11-coordinate geometry to two equivalent U(1), two equivalent Ni(1), two equivalent Ga(2), and five equivalent Ga(1) atoms. In the second Ga site, Ga(2) is bonded to four equivalent U(1) and eight equivalent Ga(1) atoms to form GaU4Ga8 cuboctahedra that share corners with four equivalent Ga(2)U4Ga8 cuboctahedra, faces with four equivalent U(1)Ga12 cuboctahedra, and faces with four equivalent Ga(2)U4Ga8 cuboctahedra.
UNiGa5 crystallizes in the tetragonal P4/mmm space group. U(1) is bonded to four equivalent Ga(2) and eight equivalent Ga(1) atoms to form UGa12 cuboctahedra that share corners with four equivalent U(1)Ga12 cuboctahedra, faces with four equivalent U(1)Ga12 cuboctahedra, and faces with four equivalent Ga(2)U4Ga8 cuboctahedra. All U(1)-Ga(2) bond lengths are 3.00 Å. All U(1)-Ga(1) bond lengths are 2.97 Å. Ni(1) is bonded in a body-centered cubic geometry to eight equivalent Ga(1) atoms. All Ni(1)-Ga(1) bond lengths are 2.49 Å. There are two inequivalent Ga sites. In the first Ga site, Ga(1) is bonded in a 11-coordinate geometry to two equivalent U(1), two equivalent Ni(1), two equivalent Ga(2), and five equivalent Ga(1) atoms. Both Ga(1)-Ga(2) bond lengths are 2.97 Å. There is one shorter (2.60 Å) and four longer (3.00 Å) Ga(1)-Ga(1) bond lengths. In the second Ga site, Ga(2) is bonded to four equivalent U(1) and eight equivalent Ga(1) atoms to form GaU4Ga8 cuboctahedra that share corners with four equivalent Ga(2)U4Ga8 cuboctahedra, faces with four equivalent U(1)Ga12 cuboctahedra, and faces with four equivalent Ga(2)U4Ga8 cuboctahedra.