CeYFe17 crystallizes in the trigonal R3m space group. Ce(1) is bonded in a 19-coordinate geometry to one Fe(5), three equivalent Fe(1), three equivalent Fe(4), six equivalent Fe(2), and six equivalent Fe(3) atoms. Y(1) is bonded in a 19-coordinate geometry to one Fe(6), three equivalent Fe(2), three equivalent Fe(4), six equivalent Fe(1), and six equivalent Fe(3) atoms. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one Ce(1), two equivalent Y(1), one Fe(6), two equivalent Fe(2), two equivalent Fe(4), and four equivalent Fe(3) atoms to form FeCeY2Fe9 cuboctahedra that share corners with two equivalent Fe(1)CeY2Fe9 cuboctahedra, corners with five equivalent Fe(4)CeYFe10 cuboctahedra, corners with eight equivalent Fe(2)Ce2YFe9 cuboctahedra,  an edgeedge with one Fe(2)Ce2YFe9 cuboctahedra, edges with three equivalent Fe(4)CeYFe10 cuboctahedra, edges with four equivalent Fe(1)CeY2Fe9 cuboctahedra, faces with three equivalent Fe(2)Ce2YFe9 cuboctahedra, faces with three equivalent Fe(4)CeYFe10 cuboctahedra, and faces with four equivalent Fe(1)CeY2Fe9 cuboctahedra. In the second Fe site, Fe(2) is bonded to two equivalent Ce(1), one Y(1), one Fe(5), two equivalent Fe(1), two equivalent Fe(4), and four equivalent Fe(3) atoms to form FeCe2YFe9 cuboctahedra that share corners with two equivalent Fe(2)Ce2YFe9 cuboctahedra, corners with five equivalent Fe(4)CeYFe10 cuboctahedra, corners with eight equivalent Fe(1)CeY2Fe9 cuboctahedra,  an edgeedge with one Fe(1)CeY2Fe9 cuboctahedra, edges with three equivalent Fe(4)CeYFe10 cuboctahedra, edges with four equivalent Fe(2)Ce2YFe9 cuboctahedra, faces with three equivalent Fe(1)CeY2Fe9 cuboctahedra, faces with three equivalent Fe(4)CeYFe10 cuboctahedra, and faces with four equivalent Fe(2)Ce2YFe9 cuboctahedra. In the third Fe site, Fe(3) is bonded in a 12-coordinate geometry to one Ce(1), one Y(1), one Fe(5), one Fe(6), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(3), and two equivalent Fe(4) atoms. In the fourth Fe site, Fe(4) is bonded to one Ce(1), one Y(1), one Fe(5), one Fe(6), two equivalent Fe(1), two equivalent Fe(2), and four equivalent Fe(3) atoms to form FeCeYFe10 cuboctahedra that share corners with four equivalent Fe(4)CeYFe10 cuboctahedra, corners with five equivalent Fe(2)Ce2YFe9 cuboctahedra, corners with five equivalent Fe(1)CeY2Fe9 cuboctahedra, edges with three equivalent Fe(2)Ce2YFe9 cuboctahedra, edges with three equivalent Fe(1)CeY2Fe9 cuboctahedra, faces with three equivalent Fe(2)Ce2YFe9 cuboctahedra, faces with three equivalent Fe(1)CeY2Fe9 cuboctahedra, and faces with four equivalent Fe(4)CeYFe10 cuboctahedra. In the fifth Fe site, Fe(5) is bonded in a 14-coordinate geometry to one Ce(1), one Fe(6), three equivalent Fe(2), three equivalent Fe(4), and six equivalent Fe(3) atoms. In the sixth Fe site, Fe(6) is bonded in a 14-coordinate geometry to one Y(1), one Fe(5), three equivalent Fe(1), three equivalent Fe(4), and six equivalent Fe(3) atoms.
CeYFe17 crystallizes in the trigonal R3m space group. Ce(1) is bonded in a 19-coordinate geometry to one Fe(5), three equivalent Fe(1), three equivalent Fe(4), six equivalent Fe(2), and six equivalent Fe(3) atoms. The Ce(1)-Fe(5) bond length is 3.07 Å. All Ce(1)-Fe(1) bond lengths are 3.06 Å. All Ce(1)-Fe(4) bond lengths are 3.31 Å. There are three shorter (3.20 Å) and three longer (3.23 Å) Ce(1)-Fe(2) bond lengths. All Ce(1)-Fe(3) bond lengths are 3.01 Å. Y(1) is bonded in a 19-coordinate geometry to one Fe(6), three equivalent Fe(2), three equivalent Fe(4), six equivalent Fe(1), and six equivalent Fe(3) atoms. The Y(1)-Fe(6) bond length is 3.05 Å. All Y(1)-Fe(2) bond lengths are 3.08 Å. All Y(1)-Fe(4) bond lengths are 3.26 Å. There are three shorter (3.19 Å) and three longer (3.24 Å) Y(1)-Fe(1) bond lengths. All Y(1)-Fe(3) bond lengths are 3.02 Å. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one Ce(1), two equivalent Y(1), one Fe(6), two equivalent Fe(2), two equivalent Fe(4), and four equivalent Fe(3) atoms to form FeCeY2Fe9 cuboctahedra that share corners with two equivalent Fe(1)CeY2Fe9 cuboctahedra, corners with five equivalent Fe(4)CeYFe10 cuboctahedra, corners with eight equivalent Fe(2)Ce2YFe9 cuboctahedra,  an edgeedge with one Fe(2)Ce2YFe9 cuboctahedra, edges with three equivalent Fe(4)CeYFe10 cuboctahedra, edges with four equivalent Fe(1)CeY2Fe9 cuboctahedra, faces with three equivalent Fe(2)Ce2YFe9 cuboctahedra, faces with three equivalent Fe(4)CeYFe10 cuboctahedra, and faces with four equivalent Fe(1)CeY2Fe9 cuboctahedra. The Fe(1)-Fe(6) bond length is 2.65 Å. Both Fe(1)-Fe(2) bond lengths are 2.46 Å. Both Fe(1)-Fe(4) bond lengths are 2.45 Å. There are two shorter (2.55 Å) and two longer (2.63 Å) Fe(1)-Fe(3) bond lengths. In the second Fe site, Fe(2) is bonded to two equivalent Ce(1), one Y(1), one Fe(5), two equivalent Fe(1), two equivalent Fe(4), and four equivalent Fe(3) atoms to form FeCe2YFe9 cuboctahedra that share corners with two equivalent Fe(2)Ce2YFe9 cuboctahedra, corners with five equivalent Fe(4)CeYFe10 cuboctahedra, corners with eight equivalent Fe(1)CeY2Fe9 cuboctahedra,  an edgeedge with one Fe(1)CeY2Fe9 cuboctahedra, edges with three equivalent Fe(4)CeYFe10 cuboctahedra, edges with four equivalent Fe(2)Ce2YFe9 cuboctahedra, faces with three equivalent Fe(1)CeY2Fe9 cuboctahedra, faces with three equivalent Fe(4)CeYFe10 cuboctahedra, and faces with four equivalent Fe(2)Ce2YFe9 cuboctahedra. The Fe(2)-Fe(5) bond length is 2.64 Å. Both Fe(2)-Fe(4) bond lengths are 2.45 Å. There are two shorter (2.56 Å) and two longer (2.62 Å) Fe(2)-Fe(3) bond lengths. In the third Fe site, Fe(3) is bonded in a 12-coordinate geometry to one Ce(1), one Y(1), one Fe(5), one Fe(6), two equivalent Fe(1), two equivalent Fe(2), two equivalent Fe(3), and two equivalent Fe(4) atoms. The Fe(3)-Fe(5) bond length is 2.77 Å. The Fe(3)-Fe(6) bond length is 2.76 Å. There is one shorter (2.48 Å) and one longer (2.49 Å) Fe(3)-Fe(3) bond length. There is one shorter (2.44 Å) and one longer (2.45 Å) Fe(3)-Fe(4) bond length. In the fourth Fe site, Fe(4) is bonded to one Ce(1), one Y(1), one Fe(5), one Fe(6), two equivalent Fe(1), two equivalent Fe(2), and four equivalent Fe(3) atoms to form FeCeYFe10 cuboctahedra that share corners with four equivalent Fe(4)CeYFe10 cuboctahedra, corners with five equivalent Fe(2)Ce2YFe9 cuboctahedra, corners with five equivalent Fe(1)CeY2Fe9 cuboctahedra, edges with three equivalent Fe(2)Ce2YFe9 cuboctahedra, edges with three equivalent Fe(1)CeY2Fe9 cuboctahedra, faces with three equivalent Fe(2)Ce2YFe9 cuboctahedra, faces with three equivalent Fe(1)CeY2Fe9 cuboctahedra, and faces with four equivalent Fe(4)CeYFe10 cuboctahedra. The Fe(4)-Fe(5) bond length is 2.60 Å. The Fe(4)-Fe(6) bond length is 2.60 Å. In the fifth Fe site, Fe(5) is bonded in a 14-coordinate geometry to one Ce(1), one Fe(6), three equivalent Fe(2), three equivalent Fe(4), and six equivalent Fe(3) atoms. The Fe(5)-Fe(6) bond length is 2.42 Å. In the sixth Fe site, Fe(6) is bonded in a 14-coordinate geometry to one Y(1), one Fe(5), three equivalent Fe(1), three equivalent Fe(4), and six equivalent Fe(3) atoms.