Nd2Co17 crystallizes in the trigonal R-3m space group. Nd(1) is bonded in a 19-coordinate geometry to one Co(1), three equivalent Co(2), six equivalent Co(3), and nine equivalent Co(4) atoms. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a 14-coordinate geometry to one Nd(1), one Co(1), three equivalent Co(2), three equivalent Co(4), and six equivalent Co(3) atoms. In the second Co site, Co(2) is bonded to two equivalent Nd(1), two equivalent Co(1), four equivalent Co(3), and four equivalent Co(4) atoms to form CoNd2Co10 cuboctahedra that share corners with four equivalent Co(2)Nd2Co10 cuboctahedra, corners with eight equivalent Co(3)Nd2Co10 cuboctahedra, corners with ten equivalent Co(4)Nd3Co9 cuboctahedra, edges with four equivalent Co(3)Nd2Co10 cuboctahedra, edges with six equivalent Co(4)Nd3Co9 cuboctahedra, faces with four equivalent Co(2)Nd2Co10 cuboctahedra, faces with six equivalent Co(4)Nd3Co9 cuboctahedra, and faces with eight equivalent Co(3)Nd2Co10 cuboctahedra. In the third Co site, Co(3) is bonded to two equivalent Nd(1), two equivalent Co(1), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(4) atoms to form distorted CoNd2Co10 cuboctahedra that share corners with four equivalent Co(2)Nd2Co10 cuboctahedra, corners with eight equivalent Co(4)Nd3Co9 cuboctahedra, corners with twelve equivalent Co(3)Nd2Co10 cuboctahedra,  an edgeedge with one Co(3)Nd2Co10 cuboctahedra, edges with two equivalent Co(2)Nd2Co10 cuboctahedra, edges with two equivalent Co(4)Nd3Co9 cuboctahedra, faces with four equivalent Co(2)Nd2Co10 cuboctahedra, faces with seven equivalent Co(3)Nd2Co10 cuboctahedra, and faces with ten equivalent Co(4)Nd3Co9 cuboctahedra. In the fourth Co site, Co(4) is bonded to three equivalent Nd(1), one Co(1), two equivalent Co(2), two equivalent Co(4), and four equivalent Co(3) atoms to form CoNd3Co9 cuboctahedra that share corners with five equivalent Co(2)Nd2Co10 cuboctahedra, corners with eight equivalent Co(3)Nd2Co10 cuboctahedra, corners with ten equivalent Co(4)Nd3Co9 cuboctahedra, edges with two equivalent Co(3)Nd2Co10 cuboctahedra, edges with three equivalent Co(2)Nd2Co10 cuboctahedra, edges with five equivalent Co(4)Nd3Co9 cuboctahedra, faces with three equivalent Co(2)Nd2Co10 cuboctahedra, faces with seven equivalent Co(4)Nd3Co9 cuboctahedra, and faces with ten equivalent Co(3)Nd2Co10 cuboctahedra.
Nd2Co17 crystallizes in the trigonal R-3m space group. Nd(1) is bonded in a 19-coordinate geometry to one Co(1), three equivalent Co(2), six equivalent Co(3), and nine equivalent Co(4) atoms. The Nd(1)-Co(1) bond length is 3.04 Å. All Nd(1)-Co(2) bond lengths are 3.24 Å. All Nd(1)-Co(3) bond lengths are 3.01 Å. There are a spread of Nd(1)-Co(4) bond distances ranging from 3.04-3.16 Å. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a 14-coordinate geometry to one Nd(1), one Co(1), three equivalent Co(2), three equivalent Co(4), and six equivalent Co(3) atoms. The Co(1)-Co(1) bond length is 2.29 Å. All Co(1)-Co(2) bond lengths are 2.57 Å. All Co(1)-Co(4) bond lengths are 2.57 Å. All Co(1)-Co(3) bond lengths are 2.64 Å. In the second Co site, Co(2) is bonded to two equivalent Nd(1), two equivalent Co(1), four equivalent Co(3), and four equivalent Co(4) atoms to form CoNd2Co10 cuboctahedra that share corners with four equivalent Co(2)Nd2Co10 cuboctahedra, corners with eight equivalent Co(3)Nd2Co10 cuboctahedra, corners with ten equivalent Co(4)Nd3Co9 cuboctahedra, edges with four equivalent Co(3)Nd2Co10 cuboctahedra, edges with six equivalent Co(4)Nd3Co9 cuboctahedra, faces with four equivalent Co(2)Nd2Co10 cuboctahedra, faces with six equivalent Co(4)Nd3Co9 cuboctahedra, and faces with eight equivalent Co(3)Nd2Co10 cuboctahedra. All Co(2)-Co(3) bond lengths are 2.38 Å. All Co(2)-Co(4) bond lengths are 2.40 Å. In the third Co site, Co(3) is bonded to two equivalent Nd(1), two equivalent Co(1), two equivalent Co(2), two equivalent Co(3), and four equivalent Co(4) atoms to form distorted CoNd2Co10 cuboctahedra that share corners with four equivalent Co(2)Nd2Co10 cuboctahedra, corners with eight equivalent Co(4)Nd3Co9 cuboctahedra, corners with twelve equivalent Co(3)Nd2Co10 cuboctahedra,  an edgeedge with one Co(3)Nd2Co10 cuboctahedra, edges with two equivalent Co(2)Nd2Co10 cuboctahedra, edges with two equivalent Co(4)Nd3Co9 cuboctahedra, faces with four equivalent Co(2)Nd2Co10 cuboctahedra, faces with seven equivalent Co(3)Nd2Co10 cuboctahedra, and faces with ten equivalent Co(4)Nd3Co9 cuboctahedra. Both Co(3)-Co(3) bond lengths are 2.38 Å. There are two shorter (2.46 Å) and two longer (2.63 Å) Co(3)-Co(4) bond lengths. In the fourth Co site, Co(4) is bonded to three equivalent Nd(1), one Co(1), two equivalent Co(2), two equivalent Co(4), and four equivalent Co(3) atoms to form CoNd3Co9 cuboctahedra that share corners with five equivalent Co(2)Nd2Co10 cuboctahedra, corners with eight equivalent Co(3)Nd2Co10 cuboctahedra, corners with ten equivalent Co(4)Nd3Co9 cuboctahedra, edges with two equivalent Co(3)Nd2Co10 cuboctahedra, edges with three equivalent Co(2)Nd2Co10 cuboctahedra, edges with five equivalent Co(4)Nd3Co9 cuboctahedra, faces with three equivalent Co(2)Nd2Co10 cuboctahedra, faces with seven equivalent Co(4)Nd3Co9 cuboctahedra, and faces with ten equivalent Co(3)Nd2Co10 cuboctahedra. Both Co(4)-Co(4) bond lengths are 2.46 Å.