Sm2Fe15Al2 crystallizes in the trigonal R-3m space group. Sm(1) is bonded in a 19-coordinate geometry to three equivalent Fe(1), six equivalent Fe(2), nine equivalent Fe(3), and one Al(1) atom. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Sm(1), four equivalent Fe(2), four equivalent Fe(3), and two equivalent Al(1) atoms to form distorted FeSm2Al2Fe8 cuboctahedra that share corners with four equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, corners with eight equivalent Fe(2)Sm2Al2Fe8 cuboctahedra, corners with ten equivalent Fe(3)Sm3AlFe8 cuboctahedra, edges with four equivalent Fe(2)Sm2Al2Fe8 cuboctahedra, edges with six equivalent Fe(3)Sm3AlFe8 cuboctahedra, faces with four equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, faces with six equivalent Fe(3)Sm3AlFe8 cuboctahedra, and faces with eight equivalent Fe(2)Sm2Al2Fe8 cuboctahedra. In the second Fe site, Fe(2) is bonded to two equivalent Sm(1), two equivalent Fe(1), two equivalent Fe(2), four equivalent Fe(3), and two equivalent Al(1) atoms to form distorted FeSm2Al2Fe8 cuboctahedra that share corners with four equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, corners with eight equivalent Fe(3)Sm3AlFe8 cuboctahedra, corners with twelve equivalent Fe(2)Sm2Al2Fe8 cuboctahedra,  an edgeedge with one Fe(2)Sm2Al2Fe8 cuboctahedra, edges with two equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, edges with two equivalent Fe(3)Sm3AlFe8 cuboctahedra, faces with four equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, faces with seven equivalent Fe(2)Sm2Al2Fe8 cuboctahedra, and faces with ten equivalent Fe(3)Sm3AlFe8 cuboctahedra. In the third Fe site, Fe(3) is bonded to three equivalent Sm(1), two equivalent Fe(1), two equivalent Fe(3), four equivalent Fe(2), and one Al(1) atom to form distorted FeSm3AlFe8 cuboctahedra that share corners with five equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, corners with eight equivalent Fe(2)Sm2Al2Fe8 cuboctahedra, corners with ten equivalent Fe(3)Sm3AlFe8 cuboctahedra, edges with two equivalent Fe(2)Sm2Al2Fe8 cuboctahedra, edges with three equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, edges with five equivalent Fe(3)Sm3AlFe8 cuboctahedra, faces with three equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, faces with seven equivalent Fe(3)Sm3AlFe8 cuboctahedra, and faces with ten equivalent Fe(2)Sm2Al2Fe8 cuboctahedra. Al(1) is bonded in a 14-coordinate geometry to one Sm(1), three equivalent Fe(1), three equivalent Fe(3), six equivalent Fe(2), and one Al(1) atom.
Sm2Fe15Al2 crystallizes in the trigonal R-3m space group. Sm(1) is bonded in a 19-coordinate geometry to three equivalent Fe(1), six equivalent Fe(2), nine equivalent Fe(3), and one Al(1) atom. All Sm(1)-Fe(1) bond lengths are 3.33 Å. All Sm(1)-Fe(2) bond lengths are 3.03 Å. There are a spread of Sm(1)-Fe(3) bond distances ranging from 3.06-3.26 Å. The Sm(1)-Al(1) bond length is 3.08 Å. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Sm(1), four equivalent Fe(2), four equivalent Fe(3), and two equivalent Al(1) atoms to form distorted FeSm2Al2Fe8 cuboctahedra that share corners with four equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, corners with eight equivalent Fe(2)Sm2Al2Fe8 cuboctahedra, corners with ten equivalent Fe(3)Sm3AlFe8 cuboctahedra, edges with four equivalent Fe(2)Sm2Al2Fe8 cuboctahedra, edges with six equivalent Fe(3)Sm3AlFe8 cuboctahedra, faces with four equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, faces with six equivalent Fe(3)Sm3AlFe8 cuboctahedra, and faces with eight equivalent Fe(2)Sm2Al2Fe8 cuboctahedra. All Fe(1)-Fe(2) bond lengths are 2.45 Å. All Fe(1)-Fe(3) bond lengths are 2.45 Å. Both Fe(1)-Al(1) bond lengths are 2.58 Å. In the second Fe site, Fe(2) is bonded to two equivalent Sm(1), two equivalent Fe(1), two equivalent Fe(2), four equivalent Fe(3), and two equivalent Al(1) atoms to form distorted FeSm2Al2Fe8 cuboctahedra that share corners with four equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, corners with eight equivalent Fe(3)Sm3AlFe8 cuboctahedra, corners with twelve equivalent Fe(2)Sm2Al2Fe8 cuboctahedra,  an edgeedge with one Fe(2)Sm2Al2Fe8 cuboctahedra, edges with two equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, edges with two equivalent Fe(3)Sm3AlFe8 cuboctahedra, faces with four equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, faces with seven equivalent Fe(2)Sm2Al2Fe8 cuboctahedra, and faces with ten equivalent Fe(3)Sm3AlFe8 cuboctahedra. Both Fe(2)-Fe(2) bond lengths are 2.47 Å. There are two shorter (2.54 Å) and two longer (2.67 Å) Fe(2)-Fe(3) bond lengths. Both Fe(2)-Al(1) bond lengths are 2.78 Å. In the third Fe site, Fe(3) is bonded to three equivalent Sm(1), two equivalent Fe(1), two equivalent Fe(3), four equivalent Fe(2), and one Al(1) atom to form distorted FeSm3AlFe8 cuboctahedra that share corners with five equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, corners with eight equivalent Fe(2)Sm2Al2Fe8 cuboctahedra, corners with ten equivalent Fe(3)Sm3AlFe8 cuboctahedra, edges with two equivalent Fe(2)Sm2Al2Fe8 cuboctahedra, edges with three equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, edges with five equivalent Fe(3)Sm3AlFe8 cuboctahedra, faces with three equivalent Fe(1)Sm2Al2Fe8 cuboctahedra, faces with seven equivalent Fe(3)Sm3AlFe8 cuboctahedra, and faces with ten equivalent Fe(2)Sm2Al2Fe8 cuboctahedra. Both Fe(3)-Fe(3) bond lengths are 2.46 Å. The Fe(3)-Al(1) bond length is 2.61 Å. Al(1) is bonded in a 14-coordinate geometry to one Sm(1), three equivalent Fe(1), three equivalent Fe(3), six equivalent Fe(2), and one Al(1) atom. The Al(1)-Al(1) bond length is 2.56 Å.