U3Tb(CoGe)8 crystallizes in the tetragonal P4/mmm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a 16-coordinate geometry to four equivalent Co(1), four equivalent Co(2), four equivalent Ge(2), and four equivalent Ge(4) atoms. In the second U site, U(2) is bonded in a 16-coordinate geometry to eight equivalent Co(2) and eight equivalent Ge(3) atoms. Tb(1) is bonded in a 16-coordinate geometry to eight equivalent Co(1) and eight equivalent Ge(1) atoms. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent U(1), two equivalent Tb(1), two equivalent Ge(1), and two equivalent Ge(4) atoms to form distorted CoTb2U2Ge4 tetrahedra that share corners with six equivalent Co(1)Tb2U2Ge4 tetrahedra, corners with six equivalent Co(2)U4Ge4 tetrahedra,  an edgeedge with one Co(2)U4Ge4 tetrahedra, edges with five equivalent Co(1)Tb2U2Ge4 tetrahedra, and faces with four equivalent Co(1)Tb2U2Ge4 tetrahedra. In the second Co site, Co(2) is bonded to two equivalent U(1), two equivalent U(2), two equivalent Ge(2), and two equivalent Ge(3) atoms to form distorted CoU4Ge4 tetrahedra that share corners with six equivalent Co(1)Tb2U2Ge4 tetrahedra, corners with six equivalent Co(2)U4Ge4 tetrahedra,  an edgeedge with one Co(1)Tb2U2Ge4 tetrahedra, edges with five equivalent Co(2)U4Ge4 tetrahedra, and faces with four equivalent Co(2)U4Ge4 tetrahedra. There are four inequivalent Ge sites. In the first Ge site, Ge(1) is bonded in a 9-coordinate geometry to four equivalent Tb(1), four equivalent Co(1), and one Ge(1) atom. In the second Ge site, Ge(2) is bonded in a 9-coordinate geometry to four equivalent U(1), four equivalent Co(2), and one Ge(4) atom. In the third Ge site, Ge(3) is bonded in a 9-coordinate geometry to four equivalent U(2), four equivalent Co(2), and one Ge(3) atom. In the fourth Ge site, Ge(4) is bonded in a 9-coordinate geometry to four equivalent U(1), four equivalent Co(1), and one Ge(2) atom.
U3Tb(CoGe)8 crystallizes in the tetragonal P4/mmm space group. There are two inequivalent U sites. In the first U site, U(1) is bonded in a 16-coordinate geometry to four equivalent Co(1), four equivalent Co(2), four equivalent Ge(2), and four equivalent Ge(4) atoms. All U(1)-Co(1) bond lengths are 3.16 Å. All U(1)-Co(2) bond lengths are 3.16 Å. All U(1)-Ge(2) bond lengths are 3.10 Å. All U(1)-Ge(4) bond lengths are 3.11 Å. In the second U site, U(2) is bonded in a 16-coordinate geometry to eight equivalent Co(2) and eight equivalent Ge(3) atoms. All U(2)-Co(2) bond lengths are 3.18 Å. All U(2)-Ge(3) bond lengths are 3.11 Å. Tb(1) is bonded in a 16-coordinate geometry to eight equivalent Co(1) and eight equivalent Ge(1) atoms. All Tb(1)-Co(1) bond lengths are 3.21 Å. All Tb(1)-Ge(1) bond lengths are 3.11 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent U(1), two equivalent Tb(1), two equivalent Ge(1), and two equivalent Ge(4) atoms to form distorted CoTb2U2Ge4 tetrahedra that share corners with six equivalent Co(1)Tb2U2Ge4 tetrahedra, corners with six equivalent Co(2)U4Ge4 tetrahedra,  an edgeedge with one Co(2)U4Ge4 tetrahedra, edges with five equivalent Co(1)Tb2U2Ge4 tetrahedra, and faces with four equivalent Co(1)Tb2U2Ge4 tetrahedra. Both Co(1)-Ge(1) bond lengths are 2.35 Å. Both Co(1)-Ge(4) bond lengths are 2.32 Å. In the second Co site, Co(2) is bonded to two equivalent U(1), two equivalent U(2), two equivalent Ge(2), and two equivalent Ge(3) atoms to form distorted CoU4Ge4 tetrahedra that share corners with six equivalent Co(1)Tb2U2Ge4 tetrahedra, corners with six equivalent Co(2)U4Ge4 tetrahedra,  an edgeedge with one Co(1)Tb2U2Ge4 tetrahedra, edges with five equivalent Co(2)U4Ge4 tetrahedra, and faces with four equivalent Co(2)U4Ge4 tetrahedra. Both Co(2)-Ge(2) bond lengths are 2.34 Å. Both Co(2)-Ge(3) bond lengths are 2.34 Å. There are four inequivalent Ge sites. In the first Ge site, Ge(1) is bonded in a 9-coordinate geometry to four equivalent Tb(1), four equivalent Co(1), and one Ge(1) atom. The Ge(1)-Ge(1) bond length is 2.55 Å. In the second Ge site, Ge(2) is bonded in a 9-coordinate geometry to four equivalent U(1), four equivalent Co(2), and one Ge(4) atom. The Ge(2)-Ge(4) bond length is 2.51 Å. In the third Ge site, Ge(3) is bonded in a 9-coordinate geometry to four equivalent U(2), four equivalent Co(2), and one Ge(3) atom. The Ge(3)-Ge(3) bond length is 2.51 Å. In the fourth Ge site, Ge(4) is bonded in a 9-coordinate geometry to four equivalent U(1), four equivalent Co(1), and one Ge(2) atom.