SmYFe17 crystallizes in the trigonal R3m space group. Sm(1) is bonded in a 19-coordinate geometry to one Fe(3), three equivalent Fe(1), three equivalent Fe(5), six equivalent Fe(2), and six equivalent Fe(6) atoms. Y(1) is bonded in a 19-coordinate geometry to one Fe(4), three equivalent Fe(1), three equivalent Fe(6), six equivalent Fe(2), and six equivalent Fe(5) atoms. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one Sm(1), one Y(1), one Fe(3), one Fe(4), two equivalent Fe(5), two equivalent Fe(6), and four equivalent Fe(2) atoms to form FeSmYFe10 cuboctahedra that share corners with four equivalent Fe(1)SmYFe10 cuboctahedra, corners with five equivalent Fe(6)Sm2YFe9 cuboctahedra, corners with five equivalent Fe(5)SmY2Fe9 cuboctahedra, edges with three equivalent Fe(6)Sm2YFe9 cuboctahedra, edges with three equivalent Fe(5)SmY2Fe9 cuboctahedra, faces with three equivalent Fe(6)Sm2YFe9 cuboctahedra, faces with three equivalent Fe(5)SmY2Fe9 cuboctahedra, and faces with four equivalent Fe(1)SmYFe10 cuboctahedra. In the second Fe site, Fe(2) is bonded in a 12-coordinate geometry to one Sm(1), one Y(1), one Fe(3), one Fe(4), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(5), and two equivalent Fe(6) atoms. In the third Fe site, Fe(3) is bonded in a 14-coordinate geometry to one Sm(1), one Fe(4), three equivalent Fe(1), three equivalent Fe(6), and six equivalent Fe(2) atoms. In the fourth Fe site, Fe(4) is bonded in a 14-coordinate geometry to one Y(1), one Fe(3), three equivalent Fe(1), three equivalent Fe(5), and six equivalent Fe(2) atoms. In the fifth Fe site, Fe(5) is bonded to one Sm(1), two equivalent Y(1), one Fe(4), two equivalent Fe(1), two equivalent Fe(6), and four equivalent Fe(2) atoms to form FeSmY2Fe9 cuboctahedra that share corners with two equivalent Fe(5)SmY2Fe9 cuboctahedra, corners with five equivalent Fe(1)SmYFe10 cuboctahedra, corners with eight equivalent Fe(6)Sm2YFe9 cuboctahedra,  an edgeedge with one Fe(6)Sm2YFe9 cuboctahedra, edges with three equivalent Fe(1)SmYFe10 cuboctahedra, edges with four equivalent Fe(5)SmY2Fe9 cuboctahedra, faces with three equivalent Fe(6)Sm2YFe9 cuboctahedra, faces with three equivalent Fe(1)SmYFe10 cuboctahedra, and faces with four equivalent Fe(5)SmY2Fe9 cuboctahedra. In the sixth Fe site, Fe(6) is bonded to two equivalent Sm(1), one Y(1), one Fe(3), two equivalent Fe(1), two equivalent Fe(5), and four equivalent Fe(2) atoms to form FeSm2YFe9 cuboctahedra that share corners with two equivalent Fe(6)Sm2YFe9 cuboctahedra, corners with five equivalent Fe(1)SmYFe10 cuboctahedra, corners with eight equivalent Fe(5)SmY2Fe9 cuboctahedra,  an edgeedge with one Fe(5)SmY2Fe9 cuboctahedra, edges with three equivalent Fe(1)SmYFe10 cuboctahedra, edges with four equivalent Fe(6)Sm2YFe9 cuboctahedra, faces with three equivalent Fe(5)SmY2Fe9 cuboctahedra, faces with three equivalent Fe(1)SmYFe10 cuboctahedra, and faces with four equivalent Fe(6)Sm2YFe9 cuboctahedra.
SmYFe17 crystallizes in the trigonal R3m space group. Sm(1) is bonded in a 19-coordinate geometry to one Fe(3), three equivalent Fe(1), three equivalent Fe(5), six equivalent Fe(2), and six equivalent Fe(6) atoms. The Sm(1)-Fe(3) bond length is 3.04 Å. All Sm(1)-Fe(1) bond lengths are 3.29 Å. All Sm(1)-Fe(5) bond lengths are 3.07 Å. All Sm(1)-Fe(2) bond lengths are 3.04 Å. There are three shorter (3.19 Å) and three longer (3.23 Å) Sm(1)-Fe(6) bond lengths. Y(1) is bonded in a 19-coordinate geometry to one Fe(4), three equivalent Fe(1), three equivalent Fe(6), six equivalent Fe(2), and six equivalent Fe(5) atoms. The Y(1)-Fe(4) bond length is 3.03 Å. All Y(1)-Fe(1) bond lengths are 3.28 Å. All Y(1)-Fe(6) bond lengths are 3.07 Å. All Y(1)-Fe(2) bond lengths are 3.03 Å. There are three shorter (3.18 Å) and three longer (3.24 Å) Y(1)-Fe(5) bond lengths. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one Sm(1), one Y(1), one Fe(3), one Fe(4), two equivalent Fe(5), two equivalent Fe(6), and four equivalent Fe(2) atoms to form FeSmYFe10 cuboctahedra that share corners with four equivalent Fe(1)SmYFe10 cuboctahedra, corners with five equivalent Fe(6)Sm2YFe9 cuboctahedra, corners with five equivalent Fe(5)SmY2Fe9 cuboctahedra, edges with three equivalent Fe(6)Sm2YFe9 cuboctahedra, edges with three equivalent Fe(5)SmY2Fe9 cuboctahedra, faces with three equivalent Fe(6)Sm2YFe9 cuboctahedra, faces with three equivalent Fe(5)SmY2Fe9 cuboctahedra, and faces with four equivalent Fe(1)SmYFe10 cuboctahedra. The Fe(1)-Fe(3) bond length is 2.61 Å. The Fe(1)-Fe(4) bond length is 2.60 Å. Both Fe(1)-Fe(5) bond lengths are 2.45 Å. Both Fe(1)-Fe(6) bond lengths are 2.46 Å. All Fe(1)-Fe(2) bond lengths are 2.43 Å. In the second Fe site, Fe(2) is bonded in a 12-coordinate geometry to one Sm(1), one Y(1), one Fe(3), one Fe(4), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(5), and two equivalent Fe(6) atoms. The Fe(2)-Fe(3) bond length is 2.76 Å. The Fe(2)-Fe(4) bond length is 2.76 Å. There is one shorter (2.47 Å) and one longer (2.49 Å) Fe(2)-Fe(2) bond length. There is one shorter (2.54 Å) and one longer (2.63 Å) Fe(2)-Fe(5) bond length. There is one shorter (2.55 Å) and one longer (2.63 Å) Fe(2)-Fe(6) bond length. In the third Fe site, Fe(3) is bonded in a 14-coordinate geometry to one Sm(1), one Fe(4), three equivalent Fe(1), three equivalent Fe(6), and six equivalent Fe(2) atoms. The Fe(3)-Fe(4) bond length is 2.41 Å. All Fe(3)-Fe(6) bond lengths are 2.65 Å. In the fourth Fe site, Fe(4) is bonded in a 14-coordinate geometry to one Y(1), one Fe(3), three equivalent Fe(1), three equivalent Fe(5), and six equivalent Fe(2) atoms. All Fe(4)-Fe(5) bond lengths are 2.64 Å. In the fifth Fe site, Fe(5) is bonded to one Sm(1), two equivalent Y(1), one Fe(4), two equivalent Fe(1), two equivalent Fe(6), and four equivalent Fe(2) atoms to form FeSmY2Fe9 cuboctahedra that share corners with two equivalent Fe(5)SmY2Fe9 cuboctahedra, corners with five equivalent Fe(1)SmYFe10 cuboctahedra, corners with eight equivalent Fe(6)Sm2YFe9 cuboctahedra,  an edgeedge with one Fe(6)Sm2YFe9 cuboctahedra, edges with three equivalent Fe(1)SmYFe10 cuboctahedra, edges with four equivalent Fe(5)SmY2Fe9 cuboctahedra, faces with three equivalent Fe(6)Sm2YFe9 cuboctahedra, faces with three equivalent Fe(1)SmYFe10 cuboctahedra, and faces with four equivalent Fe(5)SmY2Fe9 cuboctahedra. Both Fe(5)-Fe(6) bond lengths are 2.48 Å. In the sixth Fe site, Fe(6) is bonded to two equivalent Sm(1), one Y(1), one Fe(3), two equivalent Fe(1), two equivalent Fe(5), and four equivalent Fe(2) atoms to form FeSm2YFe9 cuboctahedra that share corners with two equivalent Fe(6)Sm2YFe9 cuboctahedra, corners with five equivalent Fe(1)SmYFe10 cuboctahedra, corners with eight equivalent Fe(5)SmY2Fe9 cuboctahedra,  an edgeedge with one Fe(5)SmY2Fe9 cuboctahedra, edges with three equivalent Fe(1)SmYFe10 cuboctahedra, edges with four equivalent Fe(6)Sm2YFe9 cuboctahedra, faces with three equivalent Fe(5)SmY2Fe9 cuboctahedra, faces with three equivalent Fe(1)SmYFe10 cuboctahedra, and faces with four equivalent Fe(6)Sm2YFe9 cuboctahedra.