U2NiC3 crystallizes in the orthorhombic Pnma space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a 6-coordinate geometry to two equivalent C(1), three equivalent C(2), and three equivalent C(3) atoms. In the second U site, U(2) is bonded in a 5-coordinate geometry to one C(3), two equivalent C(2), and four equivalent C(1) atoms. Ni(1) is bonded in a 3-coordinate geometry to two equivalent C(1) and two equivalent C(3) atoms. There are three inequivalent C sites. In the first C site, C(1) is bonded in a 9-coordinate geometry to two equivalent U(1), four equivalent U(2), two equivalent Ni(1), and one C(2) atom. In the second C site, C(2) is bonded to two equivalent U(2), three equivalent U(1), and one C(1) atom to form edge-sharing CU5C octahedra. In the third C site, C(3) is bonded in a 6-coordinate geometry to one U(2), three equivalent U(1), and two equivalent Ni(1) atoms.
U2NiC3 crystallizes in the orthorhombic Pnma space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a 6-coordinate geometry to two equivalent C(1), three equivalent C(2), and three equivalent C(3) atoms. Both U(1)-C(1) bond lengths are 2.76 Å. There is one shorter (2.36 Å) and two longer (2.50 Å) U(1)-C(2) bond lengths. There is one shorter (2.43 Å) and two longer (2.51 Å) U(1)-C(3) bond lengths. In the second U site, U(2) is bonded in a 5-coordinate geometry to one C(3), two equivalent C(2), and four equivalent C(1) atoms. The U(2)-C(3) bond length is 2.33 Å. Both U(2)-C(2) bond lengths are 2.48 Å. There are two shorter (2.64 Å) and two longer (2.67 Å) U(2)-C(1) bond lengths. Ni(1) is bonded in a 3-coordinate geometry to two equivalent C(1) and two equivalent C(3) atoms. There is one shorter (2.12 Å) and one longer (2.51 Å) Ni(1)-C(1) bond length. Both Ni(1)-C(3) bond lengths are 2.04 Å. There are three inequivalent C sites. In the first C site, C(1) is bonded in a 9-coordinate geometry to two equivalent U(1), four equivalent U(2), two equivalent Ni(1), and one C(2) atom. The C(1)-C(2) bond length is 1.46 Å. In the second C site, C(2) is bonded to two equivalent U(2), three equivalent U(1), and one C(1) atom to form edge-sharing CU5C octahedra. In the third C site, C(3) is bonded in a 6-coordinate geometry to one U(2), three equivalent U(1), and two equivalent Ni(1) atoms.