CeMn2Cu9 crystallizes in the tetragonal P4/mbm space group. Ce(1) is bonded in a 20-coordinate geometry to four equivalent Mn(1), eight equivalent Cu(1), and eight equivalent Cu(2) atoms. Mn(1) is bonded in a 15-coordinate geometry to two equivalent Ce(1), one Mn(1), two equivalent Cu(3), four equivalent Cu(2), and six equivalent Cu(1) atoms. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent Ce(1), three equivalent Mn(1), one Cu(3), two equivalent Cu(1), and four equivalent Cu(2) atoms to form distorted CuCe2Mn3Cu7 cuboctahedra that share  a cornercorner with one Cu(3)Mn4Cu8 cuboctahedra, corners with six equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra, corners with eleven equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra, edges with four equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra, edges with five equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra, faces with three equivalent Cu(3)Mn4Cu8 cuboctahedra, faces with seven equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra, and faces with ten equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra. In the second Cu site, Cu(2) is bonded to two equivalent Ce(1), two equivalent Mn(1), one Cu(3), three equivalent Cu(2), and four equivalent Cu(1) atoms to form distorted CuCe2Mn2Cu8 cuboctahedra that share corners with three equivalent Cu(3)Mn4Cu8 cuboctahedra, corners with six equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra, corners with eleven equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra, edges with two equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra, edges with four equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra, faces with two equivalent Cu(3)Mn4Cu8 cuboctahedra, faces with seven equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra, and faces with ten equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra. In the third Cu site, Cu(3) is bonded to four equivalent Mn(1), four equivalent Cu(1), and four equivalent Cu(2) atoms to form CuMn4Cu8 cuboctahedra that share corners with four equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra, corners with twelve equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra, edges with two equivalent Cu(3)Mn4Cu8 cuboctahedra, faces with eight equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra, and faces with twelve equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra.
CeMn2Cu9 crystallizes in the tetragonal P4/mbm space group. Ce(1) is bonded in a 20-coordinate geometry to four equivalent Mn(1), eight equivalent Cu(1), and eight equivalent Cu(2) atoms. All Ce(1)-Mn(1) bond lengths are 3.33 Å. All Ce(1)-Cu(1) bond lengths are 3.27 Å. All Ce(1)-Cu(2) bond lengths are 3.06 Å. Mn(1) is bonded in a 15-coordinate geometry to two equivalent Ce(1), one Mn(1), two equivalent Cu(3), four equivalent Cu(2), and six equivalent Cu(1) atoms. The Mn(1)-Mn(1) bond length is 2.72 Å. Both Mn(1)-Cu(3) bond lengths are 2.81 Å. All Mn(1)-Cu(2) bond lengths are 2.88 Å. There are two shorter (2.68 Å) and four longer (2.76 Å) Mn(1)-Cu(1) bond lengths. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent Ce(1), three equivalent Mn(1), one Cu(3), two equivalent Cu(1), and four equivalent Cu(2) atoms to form distorted CuCe2Mn3Cu7 cuboctahedra that share  a cornercorner with one Cu(3)Mn4Cu8 cuboctahedra, corners with six equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra, corners with eleven equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra, edges with four equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra, edges with five equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra, faces with three equivalent Cu(3)Mn4Cu8 cuboctahedra, faces with seven equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra, and faces with ten equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra. The Cu(1)-Cu(3) bond length is 2.45 Å. There is one shorter (2.36 Å) and one longer (2.55 Å) Cu(1)-Cu(1) bond length. There are two shorter (2.49 Å) and two longer (2.56 Å) Cu(1)-Cu(2) bond lengths. In the second Cu site, Cu(2) is bonded to two equivalent Ce(1), two equivalent Mn(1), one Cu(3), three equivalent Cu(2), and four equivalent Cu(1) atoms to form distorted CuCe2Mn2Cu8 cuboctahedra that share corners with three equivalent Cu(3)Mn4Cu8 cuboctahedra, corners with six equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra, corners with eleven equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra, edges with two equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra, edges with four equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra, faces with two equivalent Cu(3)Mn4Cu8 cuboctahedra, faces with seven equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra, and faces with ten equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra. The Cu(2)-Cu(3) bond length is 2.46 Å. There are two shorter (2.58 Å) and one longer (2.64 Å) Cu(2)-Cu(2) bond length. In the third Cu site, Cu(3) is bonded to four equivalent Mn(1), four equivalent Cu(1), and four equivalent Cu(2) atoms to form CuMn4Cu8 cuboctahedra that share corners with four equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra, corners with twelve equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra, edges with two equivalent Cu(3)Mn4Cu8 cuboctahedra, faces with eight equivalent Cu(2)Ce2Mn2Cu8 cuboctahedra, and faces with twelve equivalent Cu(1)Ce2Mn3Cu7 cuboctahedra.