LaYCo10 crystallizes in the orthorhombic Pmm2 space group. La(1) is bonded in a 9-coordinate geometry to two equivalent La(1), one Co(6), two equivalent Co(1), two equivalent Co(2), and two equivalent Co(3) atoms. Y(1) is bonded in a 6-coordinate geometry to two equivalent Y(1), one Co(5), two equivalent Co(2), two equivalent Co(3), and two equivalent Co(4) atoms. There are six inequivalent Co sites. In the first Co site, Co(1) is bonded in a 6-coordinate geometry to one La(1), one Co(3), one Co(4), one Co(5), and two equivalent Co(1) atoms. In the second Co site, Co(2) is bonded in a 8-coordinate geometry to one La(1), one Y(1), one Co(3), one Co(4), one Co(6), and three equivalent Co(2) atoms. In the third Co site, Co(3) is bonded to one La(1), one Y(1), one Co(1), one Co(2), one Co(5), and two equivalent Co(3) atoms to form distorted CoLaYCo5 pentagonal bipyramids that share corners with three equivalent Co(3)LaYCo5 pentagonal bipyramids, corners with two equivalent Co(4)YCo5 pentagonal pyramids, edges with three equivalent Co(5)YCo6 hexagonal pyramids,  an edgeedge with one Co(3)LaYCo5 pentagonal bipyramid, and  an edgeedge with one Co(4)YCo5 pentagonal pyramid. In the fourth Co site, Co(4) is bonded to one Y(1), one Co(1), one Co(2), one Co(6), and two equivalent Co(4) atoms to form distorted CoYCo5 pentagonal pyramids that share corners with two equivalent Co(5)YCo6 hexagonal pyramids, corners with two equivalent Co(3)LaYCo5 pentagonal bipyramids, corners with four equivalent Co(4)YCo5 pentagonal pyramids, and  an edgeedge with one Co(3)LaYCo5 pentagonal bipyramid. In the fifth Co site, Co(5) is bonded to one Y(1), two equivalent Co(1), two equivalent Co(3), and two equivalent Co(5) atoms to form distorted CoYCo6 hexagonal pyramids that share corners with two equivalent Co(5)YCo6 hexagonal pyramids, corners with four equivalent Co(4)YCo5 pentagonal pyramids, and edges with six equivalent Co(3)LaYCo5 pentagonal bipyramids. In the sixth Co site, Co(6) is bonded in a 7-coordinate geometry to one La(1), two equivalent Co(2), two equivalent Co(4), and two equivalent Co(6) atoms.
LaYCo10 crystallizes in the orthorhombic Pmm2 space group. La(1) is bonded in a 9-coordinate geometry to two equivalent La(1), one Co(6), two equivalent Co(1), two equivalent Co(2), and two equivalent Co(3) atoms. Both La(1)-La(1) bond lengths are 2.56 Å. The La(1)-Co(6) bond length is 3.07 Å. Both La(1)-Co(1) bond lengths are 2.71 Å. Both La(1)-Co(2) bond lengths are 3.25 Å. Both La(1)-Co(3) bond lengths are 2.76 Å. Y(1) is bonded in a 6-coordinate geometry to two equivalent Y(1), one Co(5), two equivalent Co(2), two equivalent Co(3), and two equivalent Co(4) atoms. Both Y(1)-Y(1) bond lengths are 2.56 Å. The Y(1)-Co(5) bond length is 3.28 Å. Both Y(1)-Co(2) bond lengths are 3.29 Å. Both Y(1)-Co(3) bond lengths are 2.75 Å. Both Y(1)-Co(4) bond lengths are 2.80 Å. There are six inequivalent Co sites. In the first Co site, Co(1) is bonded in a 6-coordinate geometry to one La(1), one Co(3), one Co(4), one Co(5), and two equivalent Co(1) atoms. The Co(1)-Co(3) bond length is 2.44 Å. The Co(1)-Co(4) bond length is 2.22 Å. The Co(1)-Co(5) bond length is 2.29 Å. Both Co(1)-Co(1) bond lengths are 2.56 Å. In the second Co site, Co(2) is bonded in a 8-coordinate geometry to one La(1), one Y(1), one Co(3), one Co(4), one Co(6), and three equivalent Co(2) atoms. The Co(2)-Co(3) bond length is 2.26 Å. The Co(2)-Co(4) bond length is 2.25 Å. The Co(2)-Co(6) bond length is 2.56 Å. There is one shorter (2.30 Å) and two longer (2.56 Å) Co(2)-Co(2) bond lengths. In the third Co site, Co(3) is bonded to one La(1), one Y(1), one Co(1), one Co(2), one Co(5), and two equivalent Co(3) atoms to form distorted CoLaYCo5 pentagonal bipyramids that share corners with three equivalent Co(3)LaYCo5 pentagonal bipyramids, corners with two equivalent Co(4)YCo5 pentagonal pyramids, edges with three equivalent Co(5)YCo6 hexagonal pyramids,  an edgeedge with one Co(3)LaYCo5 pentagonal bipyramid, and  an edgeedge with one Co(4)YCo5 pentagonal pyramid. The Co(3)-Co(5) bond length is 2.37 Å. Both Co(3)-Co(3) bond lengths are 2.56 Å. In the fourth Co site, Co(4) is bonded to one Y(1), one Co(1), one Co(2), one Co(6), and two equivalent Co(4) atoms to form distorted CoYCo5 pentagonal pyramids that share corners with two equivalent Co(5)YCo6 hexagonal pyramids, corners with two equivalent Co(3)LaYCo5 pentagonal bipyramids, corners with four equivalent Co(4)YCo5 pentagonal pyramids, and  an edgeedge with one Co(3)LaYCo5 pentagonal bipyramid. The Co(4)-Co(6) bond length is 2.34 Å. Both Co(4)-Co(4) bond lengths are 2.56 Å. In the fifth Co site, Co(5) is bonded to one Y(1), two equivalent Co(1), two equivalent Co(3), and two equivalent Co(5) atoms to form distorted CoYCo6 hexagonal pyramids that share corners with two equivalent Co(5)YCo6 hexagonal pyramids, corners with four equivalent Co(4)YCo5 pentagonal pyramids, and edges with six equivalent Co(3)LaYCo5 pentagonal bipyramids. Both Co(5)-Co(5) bond lengths are 2.56 Å. In the sixth Co site, Co(6) is bonded in a 7-coordinate geometry to one La(1), two equivalent Co(2), two equivalent Co(4), and two equivalent Co(6) atoms. Both Co(6)-Co(6) bond lengths are 2.56 Å.