U3Ga2Si3 crystallizes in the tetragonal I4cm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a 8-coordinate geometry to three equivalent Ga(1), two equivalent Si(2), and three equivalent Si(1) atoms. In the second U site, U(2) is bonded in a 10-coordinate geometry to four equivalent Ga(1), two equivalent Si(2), and four equivalent Si(1) atoms. Ga(1) is bonded in a 8-coordinate geometry to two equivalent U(2), three equivalent U(1), and three equivalent Si(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to two equivalent U(2), three equivalent U(1), and three equivalent Ga(1) atoms. In the second Si site, Si(2) is bonded to two equivalent U(2) and four equivalent U(1) atoms to form corner-sharing SiU6 octahedra. The corner-sharing octahedral tilt angles range from 0-42°.
U3Ga2Si3 crystallizes in the tetragonal I4cm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a 8-coordinate geometry to three equivalent Ga(1), two equivalent Si(2), and three equivalent Si(1) atoms. There is one shorter (3.01 Å) and two longer (3.08 Å) U(1)-Ga(1) bond lengths. Both U(1)-Si(2) bond lengths are 2.88 Å. There is one shorter (2.92 Å) and two longer (3.04 Å) U(1)-Si(1) bond lengths. In the second U site, U(2) is bonded in a 10-coordinate geometry to four equivalent Ga(1), two equivalent Si(2), and four equivalent Si(1) atoms. All U(2)-Ga(1) bond lengths are 3.06 Å. Both U(2)-Si(2) bond lengths are 2.72 Å. All U(2)-Si(1) bond lengths are 2.95 Å. Ga(1) is bonded in a 8-coordinate geometry to two equivalent U(2), three equivalent U(1), and three equivalent Si(1) atoms. There are two shorter (2.58 Å) and one longer (2.65 Å) Ga(1)-Si(1) bond length. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to two equivalent U(2), three equivalent U(1), and three equivalent Ga(1) atoms. In the second Si site, Si(2) is bonded to two equivalent U(2) and four equivalent U(1) atoms to form corner-sharing SiU6 octahedra. The corner-sharing octahedral tilt angles range from 0-42°.