UCo10Si2 crystallizes in the orthorhombic Fmmm space group. U(1) is bonded in a 20-coordinate geometry to four equivalent Co(1), four equivalent Co(3), eight equivalent Co(2), and four equivalent Si(1) atoms. There are three inequivalent Co sites. In the first Co site, Co(1) is bonded in a 10-coordinate geometry to one U(1), one Co(1), two equivalent Co(3), four equivalent Co(2), and two equivalent Si(1) atoms. In the second Co site, Co(2) is bonded in a 12-coordinate geometry to two equivalent U(1), two equivalent Co(2), two equivalent Co(3), four equivalent Co(1), and two equivalent Si(1) atoms. In the third Co site, Co(3) is bonded to two equivalent U(1), two equivalent Co(3), four equivalent Co(1), and four equivalent Co(2) atoms to form CoU2Co10 cuboctahedra that share corners with four equivalent Si(1)U2Co8Si2 cuboctahedra, corners with six equivalent Co(3)U2Co10 cuboctahedra, edges with four equivalent Si(1)U2Co8Si2 cuboctahedra, faces with two equivalent Co(3)U2Co10 cuboctahedra, and faces with four equivalent Si(1)U2Co8Si2 cuboctahedra. Si(1) is bonded to two equivalent U(1), four equivalent Co(1), four equivalent Co(2), and two equivalent Si(1) atoms to form distorted SiU2Co8Si2 cuboctahedra that share corners with four equivalent Co(3)U2Co10 cuboctahedra, corners with six equivalent Si(1)U2Co8Si2 cuboctahedra, edges with four equivalent Co(3)U2Co10 cuboctahedra, faces with two equivalent Si(1)U2Co8Si2 cuboctahedra, and faces with four equivalent Co(3)U2Co10 cuboctahedra.
UCo10Si2 crystallizes in the orthorhombic Fmmm space group. U(1) is bonded in a 20-coordinate geometry to four equivalent Co(1), four equivalent Co(3), eight equivalent Co(2), and four equivalent Si(1) atoms. All U(1)-Co(1) bond lengths are 2.82 Å. All U(1)-Co(3) bond lengths are 3.08 Å. All U(1)-Co(2) bond lengths are 3.04 Å. All U(1)-Si(1) bond lengths are 3.15 Å. There are three inequivalent Co sites. In the first Co site, Co(1) is bonded in a 10-coordinate geometry to one U(1), one Co(1), two equivalent Co(3), four equivalent Co(2), and two equivalent Si(1) atoms. The Co(1)-Co(1) bond length is 2.48 Å. Both Co(1)-Co(3) bond lengths are 2.52 Å. There are a spread of Co(1)-Co(2) bond distances ranging from 2.53-2.61 Å. Both Co(1)-Si(1) bond lengths are 2.46 Å. In the second Co site, Co(2) is bonded in a 12-coordinate geometry to two equivalent U(1), two equivalent Co(2), two equivalent Co(3), four equivalent Co(1), and two equivalent Si(1) atoms. There is one shorter (2.54 Å) and one longer (2.66 Å) Co(2)-Co(2) bond length. Both Co(2)-Co(3) bond lengths are 2.38 Å. Both Co(2)-Si(1) bond lengths are 2.36 Å. In the third Co site, Co(3) is bonded to two equivalent U(1), two equivalent Co(3), four equivalent Co(1), and four equivalent Co(2) atoms to form CoU2Co10 cuboctahedra that share corners with four equivalent Si(1)U2Co8Si2 cuboctahedra, corners with six equivalent Co(3)U2Co10 cuboctahedra, edges with four equivalent Si(1)U2Co8Si2 cuboctahedra, faces with two equivalent Co(3)U2Co10 cuboctahedra, and faces with four equivalent Si(1)U2Co8Si2 cuboctahedra. Both Co(3)-Co(3) bond lengths are 2.42 Å. Si(1) is bonded to two equivalent U(1), four equivalent Co(1), four equivalent Co(2), and two equivalent Si(1) atoms to form distorted SiU2Co8Si2 cuboctahedra that share corners with four equivalent Co(3)U2Co10 cuboctahedra, corners with six equivalent Si(1)U2Co8Si2 cuboctahedra, edges with four equivalent Co(3)U2Co10 cuboctahedra, faces with two equivalent Si(1)U2Co8Si2 cuboctahedra, and faces with four equivalent Co(3)U2Co10 cuboctahedra. Both Si(1)-Si(1) bond lengths are 2.42 Å.