U3Ni4Si4 crystallizes in the orthorhombic Immm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded to four equivalent Ni(2) and eight equivalent Si(1) atoms to form a mixture of face and edge-sharing USi8Ni4 cuboctahedra. In the second U site, U(2) is bonded in a 14-coordinate geometry to four equivalent Ni(1), four equivalent Ni(2), two equivalent Si(1), and four equivalent Si(2) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to four equivalent U(2), four equivalent Ni(1), and four equivalent Si(2) atoms to form a mixture of distorted face and corner-sharing NiU4Si4Ni4 cuboctahedra. In the second Ni site, Ni(2) is bonded in a 9-coordinate geometry to two equivalent U(1), four equivalent U(2), one Si(2), and two equivalent Si(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent U(2), four equivalent U(1), two equivalent Ni(2), and one Si(1) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to four equivalent U(2), one Ni(2), and four equivalent Ni(1) atoms.
U3Ni4Si4 crystallizes in the orthorhombic Immm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded to four equivalent Ni(2) and eight equivalent Si(1) atoms to form a mixture of face and edge-sharing USi8Ni4 cuboctahedra. All U(1)-Ni(2) bond lengths are 3.01 Å. All U(1)-Si(1) bond lengths are 2.99 Å. In the second U site, U(2) is bonded in a 14-coordinate geometry to four equivalent Ni(1), four equivalent Ni(2), two equivalent Si(1), and four equivalent Si(2) atoms. There are two shorter (3.10 Å) and two longer (3.14 Å) U(2)-Ni(1) bond lengths. All U(2)-Ni(2) bond lengths are 2.97 Å. Both U(2)-Si(1) bond lengths are 2.97 Å. All U(2)-Si(2) bond lengths are 2.99 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to four equivalent U(2), four equivalent Ni(1), and four equivalent Si(2) atoms to form a mixture of distorted face and corner-sharing NiU4Si4Ni4 cuboctahedra. All Ni(1)-Ni(1) bond lengths are 2.75 Å. There are two shorter (2.30 Å) and two longer (2.33 Å) Ni(1)-Si(2) bond lengths. In the second Ni site, Ni(2) is bonded in a 9-coordinate geometry to two equivalent U(1), four equivalent U(2), one Si(2), and two equivalent Si(1) atoms. The Ni(2)-Si(2) bond length is 2.30 Å. Both Ni(2)-Si(1) bond lengths are 2.28 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent U(2), four equivalent U(1), two equivalent Ni(2), and one Si(1) atom. The Si(1)-Si(1) bond length is 2.35 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to four equivalent U(2), one Ni(2), and four equivalent Ni(1) atoms.