U3Fe2Si7 crystallizes in the orthorhombic Cmmm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded to four equivalent Si(2), four equivalent Si(3), and four equivalent Si(4) atoms to form a mixture of distorted corner and face-sharing USi12 cuboctahedra. In the second U site, U(2) is bonded in a 14-coordinate geometry to four equivalent Fe(1), two equivalent Si(2), two equivalent Si(3), and six equivalent Si(1) atoms. Fe(1) is bonded in a 5-coordinate geometry to four equivalent U(2), one Si(1), two equivalent Si(2), and two equivalent Si(3) atoms. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to six equivalent U(2), one Fe(1), and two equivalent Si(1) atoms. In the second Si site, Si(2) is bonded in a 2-coordinate geometry to two equivalent U(1), two equivalent U(2), and two equivalent Fe(1) atoms. In the third Si site, Si(3) is bonded in a 2-coordinate geometry to two equivalent U(1), two equivalent U(2), and two equivalent Fe(1) atoms. In the fourth Si site, Si(4) is bonded in a square co-planar geometry to four equivalent U(1) atoms.
U3Fe2Si7 crystallizes in the orthorhombic Cmmm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded to four equivalent Si(2), four equivalent Si(3), and four equivalent Si(4) atoms to form a mixture of distorted corner and face-sharing USi12 cuboctahedra. All U(1)-Si(2) bond lengths are 2.92 Å. All U(1)-Si(3) bond lengths are 2.92 Å. All U(1)-Si(4) bond lengths are 2.82 Å. In the second U site, U(2) is bonded in a 14-coordinate geometry to four equivalent Fe(1), two equivalent Si(2), two equivalent Si(3), and six equivalent Si(1) atoms. All U(2)-Fe(1) bond lengths are 3.13 Å. Both U(2)-Si(2) bond lengths are 3.11 Å. Both U(2)-Si(3) bond lengths are 3.11 Å. There are four shorter (2.98 Å) and two longer (3.10 Å) U(2)-Si(1) bond lengths. Fe(1) is bonded in a 5-coordinate geometry to four equivalent U(2), one Si(1), two equivalent Si(2), and two equivalent Si(3) atoms. The Fe(1)-Si(1) bond length is 2.30 Å. Both Fe(1)-Si(2) bond lengths are 2.25 Å. Both Fe(1)-Si(3) bond lengths are 2.26 Å. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to six equivalent U(2), one Fe(1), and two equivalent Si(1) atoms. Both Si(1)-Si(1) bond lengths are 2.45 Å. In the second Si site, Si(2) is bonded in a 2-coordinate geometry to two equivalent U(1), two equivalent U(2), and two equivalent Fe(1) atoms. In the third Si site, Si(3) is bonded in a 2-coordinate geometry to two equivalent U(1), two equivalent U(2), and two equivalent Fe(1) atoms. In the fourth Si site, Si(4) is bonded in a square co-planar geometry to four equivalent U(1) atoms.