SmPrCo17 crystallizes in the trigonal R3m space group. Sm(1) is bonded in a 19-coordinate geometry to one Co(6), three equivalent Co(3), three equivalent Co(4), six equivalent Co(1), and six equivalent Co(2) atoms. Pr(1) is bonded in a 19-coordinate geometry to one Co(5), three equivalent Co(2), three equivalent Co(4), six equivalent Co(1), and six equivalent Co(3) atoms. There are six inequivalent Co sites. In the first Co site, Co(1) is bonded in a 12-coordinate geometry to one Sm(1), one Pr(1), one Co(5), one Co(6), two equivalent Co(1), two equivalent Co(2), two equivalent Co(3), and two equivalent Co(4) atoms. In the second Co site, Co(2) is bonded to two equivalent Sm(1), one Pr(1), one Co(6), two equivalent Co(3), two equivalent Co(4), and four equivalent Co(1) atoms to form CoPrSm2Co9 cuboctahedra that share corners with two equivalent Co(2)PrSm2Co9 cuboctahedra, corners with five equivalent Co(4)PrSmCo10 cuboctahedra, corners with eight equivalent Co(3)Pr2SmCo9 cuboctahedra,  an edgeedge with one Co(3)Pr2SmCo9 cuboctahedra, edges with three equivalent Co(4)PrSmCo10 cuboctahedra, edges with four equivalent Co(2)PrSm2Co9 cuboctahedra, faces with three equivalent Co(3)Pr2SmCo9 cuboctahedra, faces with three equivalent Co(4)PrSmCo10 cuboctahedra, and faces with four equivalent Co(2)PrSm2Co9 cuboctahedra. In the third Co site, Co(3) is bonded to one Sm(1), two equivalent Pr(1), one Co(5), two equivalent Co(2), two equivalent Co(4), and four equivalent Co(1) atoms to form CoPr2SmCo9 cuboctahedra that share corners with two equivalent Co(3)Pr2SmCo9 cuboctahedra, corners with five equivalent Co(4)PrSmCo10 cuboctahedra, corners with eight equivalent Co(2)PrSm2Co9 cuboctahedra,  an edgeedge with one Co(2)PrSm2Co9 cuboctahedra, edges with three equivalent Co(4)PrSmCo10 cuboctahedra, edges with four equivalent Co(3)Pr2SmCo9 cuboctahedra, faces with three equivalent Co(2)PrSm2Co9 cuboctahedra, faces with three equivalent Co(4)PrSmCo10 cuboctahedra, and faces with four equivalent Co(3)Pr2SmCo9 cuboctahedra. In the fourth Co site, Co(4) is bonded to one Sm(1), one Pr(1), one Co(5), one Co(6), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(1) atoms to form CoPrSmCo10 cuboctahedra that share corners with four equivalent Co(4)PrSmCo10 cuboctahedra, corners with five equivalent Co(3)Pr2SmCo9 cuboctahedra, corners with five equivalent Co(2)PrSm2Co9 cuboctahedra, edges with three equivalent Co(3)Pr2SmCo9 cuboctahedra, edges with three equivalent Co(2)PrSm2Co9 cuboctahedra, faces with three equivalent Co(3)Pr2SmCo9 cuboctahedra, faces with three equivalent Co(2)PrSm2Co9 cuboctahedra, and faces with four equivalent Co(4)PrSmCo10 cuboctahedra. In the fifth Co site, Co(5) is bonded in a 14-coordinate geometry to one Pr(1), one Co(6), three equivalent Co(3), three equivalent Co(4), and six equivalent Co(1) atoms. In the sixth Co site, Co(6) is bonded in a 14-coordinate geometry to one Sm(1), one Co(5), three equivalent Co(2), three equivalent Co(4), and six equivalent Co(1) atoms.
SmPrCo17 crystallizes in the trigonal R3m space group. Sm(1) is bonded in a 19-coordinate geometry to one Co(6), three equivalent Co(3), three equivalent Co(4), six equivalent Co(1), and six equivalent Co(2) atoms. The Sm(1)-Co(6) bond length is 3.01 Å. All Sm(1)-Co(3) bond lengths are 3.00 Å. All Sm(1)-Co(4) bond lengths are 3.23 Å. All Sm(1)-Co(1) bond lengths are 3.02 Å. There are three shorter (3.11 Å) and three longer (3.20 Å) Sm(1)-Co(2) bond lengths. Pr(1) is bonded in a 19-coordinate geometry to one Co(5), three equivalent Co(2), three equivalent Co(4), six equivalent Co(1), and six equivalent Co(3) atoms. The Pr(1)-Co(5) bond length is 3.03 Å. All Pr(1)-Co(2) bond lengths are 3.00 Å. All Pr(1)-Co(4) bond lengths are 3.26 Å. All Pr(1)-Co(1) bond lengths are 3.02 Å. There are three shorter (3.12 Å) and three longer (3.19 Å) Pr(1)-Co(3) bond lengths. There are six inequivalent Co sites. In the first Co site, Co(1) is bonded in a 12-coordinate geometry to one Sm(1), one Pr(1), one Co(5), one Co(6), two equivalent Co(1), two equivalent Co(2), two equivalent Co(3), and two equivalent Co(4) atoms. The Co(1)-Co(5) bond length is 2.65 Å. The Co(1)-Co(6) bond length is 2.65 Å. There is one shorter (2.37 Å) and one longer (2.39 Å) Co(1)-Co(1) bond length. There is one shorter (2.50 Å) and one longer (2.60 Å) Co(1)-Co(2) bond length. There is one shorter (2.51 Å) and one longer (2.59 Å) Co(1)-Co(3) bond length. There is one shorter (2.37 Å) and one longer (2.38 Å) Co(1)-Co(4) bond length. In the second Co site, Co(2) is bonded to two equivalent Sm(1), one Pr(1), one Co(6), two equivalent Co(3), two equivalent Co(4), and four equivalent Co(1) atoms to form CoPrSm2Co9 cuboctahedra that share corners with two equivalent Co(2)PrSm2Co9 cuboctahedra, corners with five equivalent Co(4)PrSmCo10 cuboctahedra, corners with eight equivalent Co(3)Pr2SmCo9 cuboctahedra,  an edgeedge with one Co(3)Pr2SmCo9 cuboctahedra, edges with three equivalent Co(4)PrSmCo10 cuboctahedra, edges with four equivalent Co(2)PrSm2Co9 cuboctahedra, faces with three equivalent Co(3)Pr2SmCo9 cuboctahedra, faces with three equivalent Co(4)PrSmCo10 cuboctahedra, and faces with four equivalent Co(2)PrSm2Co9 cuboctahedra. The Co(2)-Co(6) bond length is 2.58 Å. Both Co(2)-Co(3) bond lengths are 2.48 Å. Both Co(2)-Co(4) bond lengths are 2.40 Å. In the third Co site, Co(3) is bonded to one Sm(1), two equivalent Pr(1), one Co(5), two equivalent Co(2), two equivalent Co(4), and four equivalent Co(1) atoms to form CoPr2SmCo9 cuboctahedra that share corners with two equivalent Co(3)Pr2SmCo9 cuboctahedra, corners with five equivalent Co(4)PrSmCo10 cuboctahedra, corners with eight equivalent Co(2)PrSm2Co9 cuboctahedra,  an edgeedge with one Co(2)PrSm2Co9 cuboctahedra, edges with three equivalent Co(4)PrSmCo10 cuboctahedra, edges with four equivalent Co(3)Pr2SmCo9 cuboctahedra, faces with three equivalent Co(2)PrSm2Co9 cuboctahedra, faces with three equivalent Co(4)PrSmCo10 cuboctahedra, and faces with four equivalent Co(3)Pr2SmCo9 cuboctahedra. The Co(3)-Co(5) bond length is 2.59 Å. Both Co(3)-Co(4) bond lengths are 2.41 Å. In the fourth Co site, Co(4) is bonded to one Sm(1), one Pr(1), one Co(5), one Co(6), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(1) atoms to form CoPrSmCo10 cuboctahedra that share corners with four equivalent Co(4)PrSmCo10 cuboctahedra, corners with five equivalent Co(3)Pr2SmCo9 cuboctahedra, corners with five equivalent Co(2)PrSm2Co9 cuboctahedra, edges with three equivalent Co(3)Pr2SmCo9 cuboctahedra, edges with three equivalent Co(2)PrSm2Co9 cuboctahedra, faces with three equivalent Co(3)Pr2SmCo9 cuboctahedra, faces with three equivalent Co(2)PrSm2Co9 cuboctahedra, and faces with four equivalent Co(4)PrSmCo10 cuboctahedra. The Co(4)-Co(5) bond length is 2.57 Å. The Co(4)-Co(6) bond length is 2.56 Å. In the fifth Co site, Co(5) is bonded in a 14-coordinate geometry to one Pr(1), one Co(6), three equivalent Co(3), three equivalent Co(4), and six equivalent Co(1) atoms. The Co(5)-Co(6) bond length is 2.33 Å. In the sixth Co site, Co(6) is bonded in a 14-coordinate geometry to one Sm(1), one Co(5), three equivalent Co(2), three equivalent Co(4), and six equivalent Co(1) atoms.