YCo5As3 crystallizes in the orthorhombic Pnma space group. Y(1) is bonded in a 17-coordinate geometry to one Co(2), one Co(4), three equivalent Co(1), three equivalent Co(3), three equivalent Co(5), two equivalent As(1), two equivalent As(2), and two equivalent As(3) atoms. There are five inequivalent Co sites. In the first Co site, Co(1) is bonded to three equivalent Y(1), one As(1), one As(2), and two equivalent As(3) atoms to form distorted CoY3As4 tetrahedra that share corners with two equivalent Co(4)YAs4 tetrahedra, corners with three equivalent Co(3)Y3As4 tetrahedra, corners with four equivalent Co(1)Y3As4 tetrahedra, edges with two equivalent Co(1)Y3As4 tetrahedra, faces with two equivalent Co(4)YAs4 tetrahedra, and faces with three equivalent Co(3)Y3As4 tetrahedra. In the second Co site, Co(2) is bonded in a 5-coordinate geometry to one Y(1), one As(2), two equivalent As(1), and two equivalent As(3) atoms. In the third Co site, Co(3) is bonded to three equivalent Y(1), one As(1), one As(3), and two equivalent As(2) atoms to form distorted CoY3As4 tetrahedra that share  a cornercorner with one Co(4)YAs4 tetrahedra, corners with three equivalent Co(1)Y3As4 tetrahedra, corners with four equivalent Co(3)Y3As4 tetrahedra, edges with two equivalent Co(3)Y3As4 tetrahedra, edges with three equivalent Co(4)YAs4 tetrahedra, and faces with three equivalent Co(1)Y3As4 tetrahedra. In the fourth Co site, Co(4) is bonded to one Y(1), one As(3), and three equivalent As(1) atoms to form distorted CoYAs4 tetrahedra that share  a cornercorner with one Co(3)Y3As4 tetrahedra, corners with two equivalent Co(1)Y3As4 tetrahedra, corners with two equivalent Co(4)YAs4 tetrahedra, edges with two equivalent Co(4)YAs4 tetrahedra, edges with three equivalent Co(3)Y3As4 tetrahedra, and faces with two equivalent Co(1)Y3As4 tetrahedra. In the fifth Co site, Co(5) is bonded in a 4-coordinate geometry to three equivalent Y(1), one As(3), and three equivalent As(2) atoms. There are three inequivalent As sites. In the first As site, As(3) is bonded in a 9-coordinate geometry to two equivalent Y(1), one Co(3), one Co(4), one Co(5), two equivalent Co(1), and two equivalent Co(2) atoms. In the second As site, As(1) is bonded in a 9-coordinate geometry to two equivalent Y(1), one Co(1), one Co(3), two equivalent Co(2), and three equivalent Co(4) atoms. In the third As site, As(2) is bonded in a 9-coordinate geometry to two equivalent Y(1), one Co(1), one Co(2), two equivalent Co(3), and three equivalent Co(5) atoms.
YCo5As3 crystallizes in the orthorhombic Pnma space group. Y(1) is bonded in a 17-coordinate geometry to one Co(2), one Co(4), three equivalent Co(1), three equivalent Co(3), three equivalent Co(5), two equivalent As(1), two equivalent As(2), and two equivalent As(3) atoms. The Y(1)-Co(2) bond length is 3.41 Å. The Y(1)-Co(4) bond length is 3.03 Å. There are two shorter (3.09 Å) and one longer (3.19 Å) Y(1)-Co(1) bond length. There is one shorter (3.15 Å) and two longer (3.24 Å) Y(1)-Co(3) bond lengths. There are two shorter (2.98 Å) and one longer (3.18 Å) Y(1)-Co(5) bond length. Both Y(1)-As(1) bond lengths are 2.92 Å. Both Y(1)-As(2) bond lengths are 2.93 Å. Both Y(1)-As(3) bond lengths are 2.88 Å. There are five inequivalent Co sites. In the first Co site, Co(1) is bonded to three equivalent Y(1), one As(1), one As(2), and two equivalent As(3) atoms to form distorted CoY3As4 tetrahedra that share corners with two equivalent Co(4)YAs4 tetrahedra, corners with three equivalent Co(3)Y3As4 tetrahedra, corners with four equivalent Co(1)Y3As4 tetrahedra, edges with two equivalent Co(1)Y3As4 tetrahedra, faces with two equivalent Co(4)YAs4 tetrahedra, and faces with three equivalent Co(3)Y3As4 tetrahedra. The Co(1)-As(1) bond length is 2.33 Å. The Co(1)-As(2) bond length is 2.36 Å. Both Co(1)-As(3) bond lengths are 2.37 Å. In the second Co site, Co(2) is bonded in a 5-coordinate geometry to one Y(1), one As(2), two equivalent As(1), and two equivalent As(3) atoms. The Co(2)-As(2) bond length is 2.39 Å. Both Co(2)-As(1) bond lengths are 2.63 Å. Both Co(2)-As(3) bond lengths are 2.58 Å. In the third Co site, Co(3) is bonded to three equivalent Y(1), one As(1), one As(3), and two equivalent As(2) atoms to form distorted CoY3As4 tetrahedra that share  a cornercorner with one Co(4)YAs4 tetrahedra, corners with three equivalent Co(1)Y3As4 tetrahedra, corners with four equivalent Co(3)Y3As4 tetrahedra, edges with two equivalent Co(3)Y3As4 tetrahedra, edges with three equivalent Co(4)YAs4 tetrahedra, and faces with three equivalent Co(1)Y3As4 tetrahedra. The Co(3)-As(1) bond length is 2.25 Å. The Co(3)-As(3) bond length is 2.32 Å. Both Co(3)-As(2) bond lengths are 2.39 Å. In the fourth Co site, Co(4) is bonded to one Y(1), one As(3), and three equivalent As(1) atoms to form distorted CoYAs4 tetrahedra that share  a cornercorner with one Co(3)Y3As4 tetrahedra, corners with two equivalent Co(1)Y3As4 tetrahedra, corners with two equivalent Co(4)YAs4 tetrahedra, edges with two equivalent Co(4)YAs4 tetrahedra, edges with three equivalent Co(3)Y3As4 tetrahedra, and faces with two equivalent Co(1)Y3As4 tetrahedra. The Co(4)-As(3) bond length is 2.26 Å. There is one shorter (2.28 Å) and two longer (2.32 Å) Co(4)-As(1) bond lengths. In the fifth Co site, Co(5) is bonded in a 4-coordinate geometry to three equivalent Y(1), one As(3), and three equivalent As(2) atoms. The Co(5)-As(3) bond length is 2.37 Å. All Co(5)-As(2) bond lengths are 2.39 Å. There are three inequivalent As sites. In the first As site, As(3) is bonded in a 9-coordinate geometry to two equivalent Y(1), one Co(3), one Co(4), one Co(5), two equivalent Co(1), and two equivalent Co(2) atoms. In the second As site, As(1) is bonded in a 9-coordinate geometry to two equivalent Y(1), one Co(1), one Co(3), two equivalent Co(2), and three equivalent Co(4) atoms. In the third As site, As(2) is bonded in a 9-coordinate geometry to two equivalent Y(1), one Co(1), one Co(2), two equivalent Co(3), and three equivalent Co(5) atoms.