YCo3 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded in a 12-coordinate geometry to three equivalent Co(4) and nine equivalent Co(1) atoms. In the second Y site, Y(2) is bonded in a 18-coordinate geometry to three equivalent Co(2), three equivalent Co(3), and twelve equivalent Co(1) atoms. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent Y(2), three equivalent Y(1), one Co(2), one Co(3), one Co(4), and four equivalent Co(1) atoms to form CoY5Co7 cuboctahedra that share corners with two equivalent Co(4)Y6Co6 cuboctahedra, corners with fifteen equivalent Co(1)Y5Co7 cuboctahedra, edges with eight equivalent Co(1)Y5Co7 cuboctahedra, faces with three equivalent Co(4)Y6Co6 cuboctahedra, and faces with eleven equivalent Co(1)Y5Co7 cuboctahedra. In the second Co site, Co(2) is bonded in a 9-coordinate geometry to three equivalent Y(2) and six equivalent Co(1) atoms. In the third Co site, Co(3) is bonded in a 9-coordinate geometry to three equivalent Y(2) and six equivalent Co(1) atoms. In the fourth Co site, Co(4) is bonded to six equivalent Y(1) and six equivalent Co(1) atoms to form CoY6Co6 cuboctahedra that share corners with twelve equivalent Co(1)Y5Co7 cuboctahedra, edges with six equivalent Co(4)Y6Co6 cuboctahedra, and faces with eighteen equivalent Co(1)Y5Co7 cuboctahedra.
YCo3 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded in a 12-coordinate geometry to three equivalent Co(4) and nine equivalent Co(1) atoms. All Y(1)-Co(4) bond lengths are 2.96 Å. There are six shorter (2.90 Å) and three longer (3.05 Å) Y(1)-Co(1) bond lengths. In the second Y site, Y(2) is bonded in a 18-coordinate geometry to three equivalent Co(2), three equivalent Co(3), and twelve equivalent Co(1) atoms. All Y(2)-Co(2) bond lengths are 2.89 Å. All Y(2)-Co(3) bond lengths are 2.89 Å. All Y(2)-Co(1) bond lengths are 3.18 Å. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent Y(2), three equivalent Y(1), one Co(2), one Co(3), one Co(4), and four equivalent Co(1) atoms to form CoY5Co7 cuboctahedra that share corners with two equivalent Co(4)Y6Co6 cuboctahedra, corners with fifteen equivalent Co(1)Y5Co7 cuboctahedra, edges with eight equivalent Co(1)Y5Co7 cuboctahedra, faces with three equivalent Co(4)Y6Co6 cuboctahedra, and faces with eleven equivalent Co(1)Y5Co7 cuboctahedra. The Co(1)-Co(2) bond length is 2.44 Å. The Co(1)-Co(3) bond length is 2.41 Å. The Co(1)-Co(4) bond length is 2.51 Å. There are two shorter (2.46 Å) and two longer (2.55 Å) Co(1)-Co(1) bond lengths. In the second Co site, Co(2) is bonded in a 9-coordinate geometry to three equivalent Y(2) and six equivalent Co(1) atoms. In the third Co site, Co(3) is bonded in a 9-coordinate geometry to three equivalent Y(2) and six equivalent Co(1) atoms. In the fourth Co site, Co(4) is bonded to six equivalent Y(1) and six equivalent Co(1) atoms to form CoY6Co6 cuboctahedra that share corners with twelve equivalent Co(1)Y5Co7 cuboctahedra, edges with six equivalent Co(4)Y6Co6 cuboctahedra, and faces with eighteen equivalent Co(1)Y5Co7 cuboctahedra.