Sm(Fe5Si)2 crystallizes in the orthorhombic Fmmm space group. Sm(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 Sm(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 Sm(1), two equivalent Fe(2), four equivalent Fe(1), and four equivalent Fe(3) atoms to form FeSm2Fe10 cuboctahedra that share corners with four equivalent Si(1)Sm2Fe8Si2 cuboctahedra, corners with six equivalent Fe(2)Sm2Fe10 cuboctahedra, corners with eight equivalent Fe(3)Sm2Fe8Si2 cuboctahedra, edges with four equivalent Fe(3)Sm2Fe8Si2 cuboctahedra, edges with four equivalent Si(1)Sm2Fe8Si2 cuboctahedra, faces with two equivalent Fe(2)Sm2Fe10 cuboctahedra, faces with four equivalent Si(1)Sm2Fe8Si2 cuboctahedra, and faces with eight equivalent Fe(3)Sm2Fe8Si2 cuboctahedra. In the third Fe site, Fe(3) is bonded to two equivalent Sm(1), two equivalent Fe(2), two equivalent Fe(3), four equivalent Fe(1), and two equivalent Si(1) atoms to form distorted FeSm2Fe8Si2 cuboctahedra that share corners with four equivalent Fe(2)Sm2Fe10 cuboctahedra, corners with four equivalent Si(1)Sm2Fe8Si2 cuboctahedra, corners with ten equivalent Fe(3)Sm2Fe8Si2 cuboctahedra, edges with two equivalent Fe(2)Sm2Fe10 cuboctahedra, edges with two equivalent Si(1)Sm2Fe8Si2 cuboctahedra, edges with three equivalent Fe(3)Sm2Fe8Si2 cuboctahedra, faces with four equivalent Fe(2)Sm2Fe10 cuboctahedra, faces with four equivalent Si(1)Sm2Fe8Si2 cuboctahedra, and faces with seven equivalent Fe(3)Sm2Fe8Si2 cuboctahedra. Si(1) is bonded to two equivalent Sm(1), four equivalent Fe(1), four equivalent Fe(3), and two equivalent Si(1) atoms to form distorted SiSm2Fe8Si2 cuboctahedra that share corners with four equivalent Fe(2)Sm2Fe10 cuboctahedra, corners with six equivalent Si(1)Sm2Fe8Si2 cuboctahedra, corners with eight equivalent Fe(3)Sm2Fe8Si2 cuboctahedra, edges with four equivalent Fe(2)Sm2Fe10 cuboctahedra, edges with four equivalent Fe(3)Sm2Fe8Si2 cuboctahedra, faces with two equivalent Si(1)Sm2Fe8Si2 cuboctahedra, faces with four equivalent Fe(2)Sm2Fe10 cuboctahedra, and faces with eight equivalent Fe(3)Sm2Fe8Si2 cuboctahedra.
Sm(Fe5Si)2 crystallizes in the orthorhombic Fmmm space group. Sm(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 Sm(1)-Fe(1) bond lengths are 2.99 Å. All Sm(1)-Fe(2) bond lengths are 3.19 Å. All Sm(1)-Fe(3) bond lengths are 3.05 Å. All Sm(1)-Si(1) bond lengths are 3.15 Å. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 14-coordinate geometry to one Sm(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 2.58 Å. There are a spread of Fe(1)-Fe(3) bond distances ranging from 2.50-2.64 Å. There are a spread of Fe(1)-Fe(1) bond distances ranging from 2.33-2.94 Å. Both Fe(1)-Si(1) bond lengths are 2.55 Å. In the second Fe site, Fe(2) is bonded to two equivalent Sm(1), two equivalent Fe(2), four equivalent Fe(1), and four equivalent Fe(3) atoms to form FeSm2Fe10 cuboctahedra that share corners with four equivalent Si(1)Sm2Fe8Si2 cuboctahedra, corners with six equivalent Fe(2)Sm2Fe10 cuboctahedra, corners with eight equivalent Fe(3)Sm2Fe8Si2 cuboctahedra, edges with four equivalent Fe(3)Sm2Fe8Si2 cuboctahedra, edges with four equivalent Si(1)Sm2Fe8Si2 cuboctahedra, faces with two equivalent Fe(2)Sm2Fe10 cuboctahedra, faces with four equivalent Si(1)Sm2Fe8Si2 cuboctahedra, and faces with eight equivalent Fe(3)Sm2Fe8Si2 cuboctahedra. Both Fe(2)-Fe(2) bond lengths are 2.40 Å. All Fe(2)-Fe(3) bond lengths are 2.41 Å. In the third Fe site, Fe(3) is bonded to two equivalent Sm(1), two equivalent Fe(2), two equivalent Fe(3), four equivalent Fe(1), and two equivalent Si(1) atoms to form distorted FeSm2Fe8Si2 cuboctahedra that share corners with four equivalent Fe(2)Sm2Fe10 cuboctahedra, corners with four equivalent Si(1)Sm2Fe8Si2 cuboctahedra, corners with ten equivalent Fe(3)Sm2Fe8Si2 cuboctahedra, edges with two equivalent Fe(2)Sm2Fe10 cuboctahedra, edges with two equivalent Si(1)Sm2Fe8Si2 cuboctahedra, edges with three equivalent Fe(3)Sm2Fe8Si2 cuboctahedra, faces with four equivalent Fe(2)Sm2Fe10 cuboctahedra, faces with four equivalent Si(1)Sm2Fe8Si2 cuboctahedra, and faces with seven equivalent Fe(3)Sm2Fe8Si2 cuboctahedra. There is one shorter (2.65 Å) and one longer (2.66 Å) Fe(3)-Fe(3) bond length. Both Fe(3)-Si(1) bond lengths are 2.40 Å. Si(1) is bonded to two equivalent Sm(1), four equivalent Fe(1), four equivalent Fe(3), and two equivalent Si(1) atoms to form distorted SiSm2Fe8Si2 cuboctahedra that share corners with four equivalent Fe(2)Sm2Fe10 cuboctahedra, corners with six equivalent Si(1)Sm2Fe8Si2 cuboctahedra, corners with eight equivalent Fe(3)Sm2Fe8Si2 cuboctahedra, edges with four equivalent Fe(2)Sm2Fe10 cuboctahedra, edges with four equivalent Fe(3)Sm2Fe8Si2 cuboctahedra, faces with two equivalent Si(1)Sm2Fe8Si2 cuboctahedra, faces with four equivalent Fe(2)Sm2Fe10 cuboctahedra, and faces with eight equivalent Fe(3)Sm2Fe8Si2 cuboctahedra. Both Si(1)-Si(1) bond lengths are 2.40 Å.