SmFe12 crystallizes in the tetragonal I4/mmm space group. Sm(1) is bonded in a 20-coordinate geometry to four equivalent Fe(2), eight equivalent Fe(1), and eight equivalent Fe(3) atoms. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Sm(1), two equivalent Fe(1), four equivalent Fe(2), and four equivalent Fe(3) atoms to form a mixture of corner, face, and edge-sharing FeSm2Fe10 cuboctahedra. In the second Fe site, Fe(3) is bonded in a 12-coordinate geometry to two equivalent Sm(1), two equivalent Fe(3), four equivalent Fe(1), and four equivalent Fe(2) atoms. In the third Fe site, Fe(2) is bonded in a 14-coordinate geometry to one Sm(1), four equivalent Fe(1), four equivalent Fe(3), and five equivalent Fe(2) atoms.
SmFe12 crystallizes in the tetragonal I4/mmm space group. Sm(1) is bonded in a 20-coordinate geometry to four equivalent Fe(2), eight equivalent Fe(1), and eight equivalent Fe(3) atoms. All Sm(1)-Fe(2) bond lengths are 3.05 Å. All Sm(1)-Fe(1) bond lengths are 3.23 Å. All Sm(1)-Fe(3) bond lengths are 3.05 Å. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Sm(1), two equivalent Fe(1), four equivalent Fe(2), and four equivalent Fe(3) atoms to form a mixture of corner, face, and edge-sharing FeSm2Fe10 cuboctahedra. Both Fe(1)-Fe(1) bond lengths are 2.33 Å. All Fe(1)-Fe(2) bond lengths are 2.60 Å. All Fe(1)-Fe(3) bond lengths are 2.43 Å. In the second Fe site, Fe(3) is bonded in a 12-coordinate geometry to two equivalent Sm(1), two equivalent Fe(3), four equivalent Fe(1), and four equivalent Fe(2) atoms. Both Fe(3)-Fe(3) bond lengths are 2.79 Å. There are two shorter (2.57 Å) and two longer (2.58 Å) Fe(3)-Fe(2) bond lengths. In the third Fe site, Fe(2) is bonded in a 14-coordinate geometry to one Sm(1), four equivalent Fe(1), four equivalent Fe(3), and five equivalent Fe(2) atoms. There is one shorter (2.40 Å) and four longer (2.89 Å) Fe(2)-Fe(2) bond lengths.