EuCo8P5 crystallizes in the orthorhombic Pmmn space group. Eu(1) is bonded in a 15-coordinate geometry to one Co(4), two equivalent Co(2), four equivalent Co(3), four equivalent P(1), and four equivalent P(2) atoms. There are five inequivalent Co sites. In the first Co site, Co(1) is bonded to one P(3) and three equivalent P(1) atoms to form distorted CoP4 tetrahedra that share  a cornercorner with one Co(2)Eu2P4 tetrahedra, corners with three equivalent Co(3)Eu2P4 tetrahedra, corners with three equivalent Co(1)P4 tetrahedra, edges with two equivalent Co(2)Eu2P4 tetrahedra, and edges with two equivalent Co(1)P4 tetrahedra. In the second Co site, Co(2) is bonded to two equivalent Eu(1), two equivalent P(1), and two equivalent P(3) atoms to form distorted CoEu2P4 tetrahedra that share corners with two equivalent Co(1)P4 tetrahedra, corners with four equivalent Co(3)Eu2P4 tetrahedra, edges with two equivalent Co(2)Eu2P4 tetrahedra, edges with four equivalent Co(1)P4 tetrahedra, and faces with two equivalent Co(3)Eu2P4 tetrahedra. In the third Co site, Co(3) is bonded to two equivalent Eu(1), one P(1), and three equivalent P(2) atoms to form distorted CoEu2P4 tetrahedra that share corners with two equivalent Co(2)Eu2P4 tetrahedra, corners with two equivalent Co(3)Eu2P4 tetrahedra, corners with three equivalent Co(1)P4 tetrahedra, edges with five equivalent Co(3)Eu2P4 tetrahedra, and  a faceface with one Co(2)Eu2P4 tetrahedra. In the fourth Co site, Co(4) is bonded in a 5-coordinate geometry to one Eu(1), one P(3), and four equivalent P(2) atoms. In the fifth Co site, Co(5) is bonded in a 5-coordinate geometry to one P(2), two equivalent P(1), and two equivalent P(3) atoms. There are three inequivalent P sites. In the first P site, P(1) is bonded in a 9-coordinate geometry to two equivalent Eu(1), one Co(2), one Co(3), two equivalent Co(5), and three equivalent Co(1) atoms. In the second P site, P(2) is bonded in a 9-coordinate geometry to two equivalent Eu(1), one Co(5), two equivalent Co(4), three equivalent Co(3), and one P(2) atom. In the third P site, P(3) is bonded in a 9-coordinate geometry to one Co(4), two equivalent Co(1), two equivalent Co(2), and four equivalent Co(5) atoms.
EuCo8P5 crystallizes in the orthorhombic Pmmn space group. Eu(1) is bonded in a 15-coordinate geometry to one Co(4), two equivalent Co(2), four equivalent Co(3), four equivalent P(1), and four equivalent P(2) atoms. The Eu(1)-Co(4) bond length is 3.03 Å. Both Eu(1)-Co(2) bond lengths are 3.14 Å. All Eu(1)-Co(3) bond lengths are 3.26 Å. All Eu(1)-P(1) bond lengths are 3.03 Å. All Eu(1)-P(2) bond lengths are 3.08 Å. There are five inequivalent Co sites. In the first Co site, Co(1) is bonded to one P(3) and three equivalent P(1) atoms to form distorted CoP4 tetrahedra that share  a cornercorner with one Co(2)Eu2P4 tetrahedra, corners with three equivalent Co(3)Eu2P4 tetrahedra, corners with three equivalent Co(1)P4 tetrahedra, edges with two equivalent Co(2)Eu2P4 tetrahedra, and edges with two equivalent Co(1)P4 tetrahedra. The Co(1)-P(3) bond length is 2.13 Å. There are two shorter (2.22 Å) and one longer (2.23 Å) Co(1)-P(1) bond length. In the second Co site, Co(2) is bonded to two equivalent Eu(1), two equivalent P(1), and two equivalent P(3) atoms to form distorted CoEu2P4 tetrahedra that share corners with two equivalent Co(1)P4 tetrahedra, corners with four equivalent Co(3)Eu2P4 tetrahedra, edges with two equivalent Co(2)Eu2P4 tetrahedra, edges with four equivalent Co(1)P4 tetrahedra, and faces with two equivalent Co(3)Eu2P4 tetrahedra. Both Co(2)-P(1) bond lengths are 2.24 Å. Both Co(2)-P(3) bond lengths are 2.26 Å. In the third Co site, Co(3) is bonded to two equivalent Eu(1), one P(1), and three equivalent P(2) atoms to form distorted CoEu2P4 tetrahedra that share corners with two equivalent Co(2)Eu2P4 tetrahedra, corners with two equivalent Co(3)Eu2P4 tetrahedra, corners with three equivalent Co(1)P4 tetrahedra, edges with five equivalent Co(3)Eu2P4 tetrahedra, and  a faceface with one Co(2)Eu2P4 tetrahedra. The Co(3)-P(1) bond length is 2.20 Å. There is one shorter (2.16 Å) and two longer (2.23 Å) Co(3)-P(2) bond lengths. In the fourth Co site, Co(4) is bonded in a 5-coordinate geometry to one Eu(1), one P(3), and four equivalent P(2) atoms. The Co(4)-P(3) bond length is 2.14 Å. All Co(4)-P(2) bond lengths are 2.32 Å. In the fifth Co site, Co(5) is bonded in a 5-coordinate geometry to one P(2), two equivalent P(1), and two equivalent P(3) atoms. The Co(5)-P(2) bond length is 2.21 Å. Both Co(5)-P(1) bond lengths are 2.49 Å. Both Co(5)-P(3) bond lengths are 2.47 Å. There are three inequivalent P sites. In the first P site, P(1) is bonded in a 9-coordinate geometry to two equivalent Eu(1), one Co(2), one Co(3), two equivalent Co(5), and three equivalent Co(1) atoms. In the second P site, P(2) is bonded in a 9-coordinate geometry to two equivalent Eu(1), one Co(5), two equivalent Co(4), three equivalent Co(3), and one P(2) atom. The P(2)-P(2) bond length is 2.47 Å. In the third P site, P(3) is bonded in a 9-coordinate geometry to one Co(4), two equivalent Co(1), two equivalent Co(2), and four equivalent Co(5) atoms.