Al11Sm3 crystallizes in the orthorhombic Immm space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded to four equivalent Al(2), four equivalent Al(4), and eight equivalent Al(3) atoms to form distorted SmAl16 cuboctahedra that share corners with four equivalent Al(1)Sm4Al8 cuboctahedra, faces with two equivalent Sm(1)Al16 cuboctahedra, faces with two equivalent Al(1)Sm4Al8 cuboctahedra, and faces with four equivalent Al(2)Sm4Al8 cuboctahedra. In the second Sm site, Sm(2) is bonded in a 12-coordinate geometry to two equivalent Al(1), two equivalent Al(2), four equivalent Al(3), and six equivalent Al(4) atoms. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to four equivalent Sm(2), four equivalent Al(2), and four equivalent Al(4) atoms to form AlSm4Al8 cuboctahedra that share corners with four equivalent Sm(1)Al16 cuboctahedra, faces with two equivalent Sm(1)Al16 cuboctahedra, faces with two equivalent Al(1)Sm4Al8 cuboctahedra, and faces with four equivalent Al(2)Sm4Al8 cuboctahedra. In the second Al site, Al(2) is bonded to two equivalent Sm(1), two equivalent Sm(2), two equivalent Al(1), two equivalent Al(3), and four equivalent Al(4) atoms to form distorted AlSm4Al8 cuboctahedra that share corners with four equivalent Al(2)Sm4Al8 cuboctahedra,  an edgeedge with one Al(2)Sm4Al8 cuboctahedra, faces with two equivalent Sm(1)Al16 cuboctahedra, faces with two equivalent Al(1)Sm4Al8 cuboctahedra, and faces with three equivalent Al(2)Sm4Al8 cuboctahedra. In the third Al site, Al(3) is bonded in a 9-coordinate geometry to two equivalent Sm(1), two equivalent Sm(2), one Al(2), one Al(3), and three equivalent Al(4) atoms. In the fourth Al site, Al(4) is bonded in a 10-coordinate geometry to one Sm(1), three equivalent Sm(2), one Al(1), two equivalent Al(2), and three equivalent Al(3) atoms.
Al11Sm3 crystallizes in the orthorhombic Immm space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded to four equivalent Al(2), four equivalent Al(4), and eight equivalent Al(3) atoms to form distorted SmAl16 cuboctahedra that share corners with four equivalent Al(1)Sm4Al8 cuboctahedra, faces with two equivalent Sm(1)Al16 cuboctahedra, faces with two equivalent Al(1)Sm4Al8 cuboctahedra, and faces with four equivalent Al(2)Sm4Al8 cuboctahedra. All Sm(1)-Al(2) bond lengths are 3.57 Å. All Sm(1)-Al(4) bond lengths are 3.23 Å. All Sm(1)-Al(3) bond lengths are 3.31 Å. In the second Sm site, Sm(2) is bonded in a 12-coordinate geometry to two equivalent Al(1), two equivalent Al(2), four equivalent Al(3), and six equivalent Al(4) atoms. Both Sm(2)-Al(1) bond lengths are 3.21 Å. Both Sm(2)-Al(2) bond lengths are 3.17 Å. All Sm(2)-Al(3) bond lengths are 3.19 Å. There are four shorter (3.17 Å) and two longer (3.58 Å) Sm(2)-Al(4) bond lengths. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to four equivalent Sm(2), four equivalent Al(2), and four equivalent Al(4) atoms to form AlSm4Al8 cuboctahedra that share corners with four equivalent Sm(1)Al16 cuboctahedra, faces with two equivalent Sm(1)Al16 cuboctahedra, faces with two equivalent Al(1)Sm4Al8 cuboctahedra, and faces with four equivalent Al(2)Sm4Al8 cuboctahedra. All Al(1)-Al(2) bond lengths are 3.02 Å. All Al(1)-Al(4) bond lengths are 2.82 Å. In the second Al site, Al(2) is bonded to two equivalent Sm(1), two equivalent Sm(2), two equivalent Al(1), two equivalent Al(3), and four equivalent Al(4) atoms to form distorted AlSm4Al8 cuboctahedra that share corners with four equivalent Al(2)Sm4Al8 cuboctahedra,  an edgeedge with one Al(2)Sm4Al8 cuboctahedra, faces with two equivalent Sm(1)Al16 cuboctahedra, faces with two equivalent Al(1)Sm4Al8 cuboctahedra, and faces with three equivalent Al(2)Sm4Al8 cuboctahedra. Both Al(2)-Al(3) bond lengths are 2.63 Å. All Al(2)-Al(4) bond lengths are 2.79 Å. In the third Al site, Al(3) is bonded in a 9-coordinate geometry to two equivalent Sm(1), two equivalent Sm(2), one Al(2), one Al(3), and three equivalent Al(4) atoms. The Al(3)-Al(3) bond length is 2.60 Å. There are two shorter (2.62 Å) and one longer (2.72 Å) Al(3)-Al(4) bond length. In the fourth Al site, Al(4) is bonded in a 10-coordinate geometry to one Sm(1), three equivalent Sm(2), one Al(1), two equivalent Al(2), and three equivalent Al(3) atoms.