LuFe10Si2 crystallizes in the orthorhombic Fmmm space group. Lu(1) is bonded in a 20-coordinate geometry to four equivalent Fe(1), four equivalent Fe(2), eight equivalent Fe(3), and four equivalent Si(1) atoms. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 14-coordinate geometry to one Lu(1), two equivalent Fe(2), four equivalent Fe(3), five equivalent Fe(1), and two equivalent Si(1) atoms. In the second Fe site, Fe(2) is bonded to two equivalent Lu(1), two equivalent Fe(2), four equivalent Fe(1), and four equivalent Fe(3) atoms to form FeLu2Fe10 cuboctahedra that share corners with four equivalent Si(1)Lu2Fe8Si2 cuboctahedra, corners with six equivalent Fe(2)Lu2Fe10 cuboctahedra, edges with four equivalent Si(1)Lu2Fe8Si2 cuboctahedra, faces with two equivalent Fe(2)Lu2Fe10 cuboctahedra, and faces with four equivalent Si(1)Lu2Fe8Si2 cuboctahedra. In the third Fe site, Fe(3) is bonded in a 12-coordinate geometry to two equivalent Lu(1), two equivalent Fe(2), two equivalent Fe(3), four equivalent Fe(1), and two equivalent Si(1) atoms. Si(1) is bonded to two equivalent Lu(1), four equivalent Fe(1), four equivalent Fe(3), and two equivalent Si(1) atoms to form distorted SiLu2Fe8Si2 cuboctahedra that share corners with four equivalent Fe(2)Lu2Fe10 cuboctahedra, corners with six equivalent Si(1)Lu2Fe8Si2 cuboctahedra, edges with four equivalent Fe(2)Lu2Fe10 cuboctahedra, faces with two equivalent Si(1)Lu2Fe8Si2 cuboctahedra, and faces with four equivalent Fe(2)Lu2Fe10 cuboctahedra.
LuFe10Si2 crystallizes in the orthorhombic Fmmm space group. Lu(1) is bonded in a 20-coordinate geometry to four equivalent Fe(1), four equivalent Fe(2), eight equivalent Fe(3), and four equivalent Si(1) atoms. All Lu(1)-Fe(1) bond lengths are 2.95 Å. All Lu(1)-Fe(2) bond lengths are 3.16 Å. All Lu(1)-Fe(3) bond lengths are 2.99 Å. All Lu(1)-Si(1) bond lengths are 3.12 Å. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 14-coordinate geometry to one Lu(1), two equivalent Fe(2), four equivalent Fe(3), five equivalent Fe(1), and two equivalent Si(1) atoms. Both Fe(1)-Fe(2) bond lengths are 2.55 Å. There are a spread of Fe(1)-Fe(3) bond distances ranging from 2.54-2.64 Å. There are a spread of Fe(1)-Fe(1) bond distances ranging from 2.33-2.93 Å. Both Fe(1)-Si(1) bond lengths are 2.53 Å. In the second Fe site, Fe(2) is bonded to two equivalent Lu(1), two equivalent Fe(2), four equivalent Fe(1), and four equivalent Fe(3) atoms to form FeLu2Fe10 cuboctahedra that share corners with four equivalent Si(1)Lu2Fe8Si2 cuboctahedra, corners with six equivalent Fe(2)Lu2Fe10 cuboctahedra, edges with four equivalent Si(1)Lu2Fe8Si2 cuboctahedra, faces with two equivalent Fe(2)Lu2Fe10 cuboctahedra, and faces with four equivalent Si(1)Lu2Fe8Si2 cuboctahedra. Both Fe(2)-Fe(2) bond lengths are 2.39 Å. All Fe(2)-Fe(3) bond lengths are 2.40 Å. In the third Fe site, Fe(3) is bonded in a 12-coordinate geometry to two equivalent Lu(1), two equivalent Fe(2), two equivalent Fe(3), four equivalent Fe(1), and two equivalent Si(1) atoms. Both Fe(3)-Fe(3) bond lengths are 2.55 Å. Both Fe(3)-Si(1) bond lengths are 2.38 Å. Si(1) is bonded to two equivalent Lu(1), four equivalent Fe(1), four equivalent Fe(3), and two equivalent Si(1) atoms to form distorted SiLu2Fe8Si2 cuboctahedra that share corners with four equivalent Fe(2)Lu2Fe10 cuboctahedra, corners with six equivalent Si(1)Lu2Fe8Si2 cuboctahedra, edges with four equivalent Fe(2)Lu2Fe10 cuboctahedra, faces with two equivalent Si(1)Lu2Fe8Si2 cuboctahedra, and faces with four equivalent Fe(2)Lu2Fe10 cuboctahedra. Both Si(1)-Si(1) bond lengths are 2.39 Å.