U3Si2C2 crystallizes in the tetragonal I4/mmm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a 5-coordinate geometry to one U(2) and five equivalent C(1) atoms. In the second U site, U(2) is bonded in a 10-coordinate geometry to two equivalent U(1) and eight equivalent Si(1) atoms. Si(1) is bonded in a single-bond geometry to four equivalent U(2) and one C(1) atom. C(1) is bonded to five equivalent U(1) and one Si(1) atom to form a mixture of distorted corner and edge-sharing CU5Si octahedra. The corner-sharing octahedral tilt angles are 18°.
U3Si2C2 crystallizes in the tetragonal I4/mmm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a 5-coordinate geometry to one U(2) and five equivalent C(1) atoms. The U(1)-U(2) bond length is 2.88 Å. There is one shorter (2.21 Å) and four longer (2.62 Å) U(1)-C(1) bond lengths. In the second U site, U(2) is bonded in a 10-coordinate geometry to two equivalent U(1) and eight equivalent Si(1) atoms. All U(2)-Si(1) bond lengths are 2.94 Å. Si(1) is bonded in a single-bond geometry to four equivalent U(2) and one C(1) atom. The Si(1)-C(1) bond length is 1.88 Å. C(1) is bonded to five equivalent U(1) and one Si(1) atom to form a mixture of distorted corner and edge-sharing CU5Si octahedra. The corner-sharing octahedral tilt angles are 18°.