Lu3Fe2Si3 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Lu sites. In the first Lu site, Lu(1) is bonded in a 9-coordinate geometry to four equivalent Fe(1), two equivalent Si(2), and three equivalent Si(1) atoms. In the second Lu site, Lu(2) is bonded in a 10-coordinate geometry to four equivalent Fe(1), two equivalent Si(1), and five equivalent Si(2) atoms. Fe(1) is bonded in a 10-coordinate geometry to two equivalent Lu(1), four equivalent Lu(2), one Si(1), and three equivalent Si(2) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to three equivalent Lu(1), four equivalent Lu(2), and two equivalent Fe(1) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to one Lu(1), five equivalent Lu(2), three equivalent Fe(1), and one Si(2) atom.
Lu3Fe2Si3 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Lu sites. In the first Lu site, Lu(1) is bonded in a 9-coordinate geometry to four equivalent Fe(1), two equivalent Si(2), and three equivalent Si(1) atoms. All Lu(1)-Fe(1) bond lengths are 3.14 Å. Both Lu(1)-Si(2) bond lengths are 2.84 Å. There are two shorter (2.85 Å) and one longer (3.11 Å) Lu(1)-Si(1) bond length. In the second Lu site, Lu(2) is bonded in a 10-coordinate geometry to four equivalent Fe(1), two equivalent Si(1), and five equivalent Si(2) atoms. There are a spread of Lu(2)-Fe(1) bond distances ranging from 2.94-3.05 Å. Both Lu(2)-Si(1) bond lengths are 2.89 Å. There are a spread of Lu(2)-Si(2) bond distances ranging from 2.90-3.24 Å. Fe(1) is bonded in a 10-coordinate geometry to two equivalent Lu(1), four equivalent Lu(2), one Si(1), and three equivalent Si(2) atoms. The Fe(1)-Si(1) bond length is 2.54 Å. There are two shorter (2.34 Å) and one longer (2.39 Å) Fe(1)-Si(2) bond length. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to three equivalent Lu(1), four equivalent Lu(2), and two equivalent Fe(1) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to one Lu(1), five equivalent Lu(2), three equivalent Fe(1), and one Si(2) atom. The Si(2)-Si(2) bond length is 2.59 Å.