Th2Au5Al8Si2 crystallizes in the orthorhombic Cmmm space group. Th(1) is bonded in a 14-coordinate geometry to four equivalent Au(1), two equivalent Al(1), two equivalent Al(2), and six equivalent Si(1) atoms. There are three inequivalent Au sites. In the first Au site, Au(1) is bonded in a 9-coordinate geometry to four equivalent Th(1), two equivalent Al(1), two equivalent Al(2), and one Si(1) atom. In the second Au site, Au(2) is bonded in a body-centered cubic geometry to four equivalent Al(3) and four equivalent Al(4) atoms. In the third Au site, Au(3) is bonded in a body-centered cubic geometry to two equivalent Al(1), two equivalent Al(2), two equivalent Al(3), and two equivalent Al(4) atoms. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to two equivalent Th(1), two equivalent Au(1), and two equivalent Au(3) atoms to form AlTh2Au4 tetrahedra that share corners with two equivalent Al(4)Au4 tetrahedra, corners with two equivalent Al(1)Th2Au4 tetrahedra, corners with four equivalent Al(3)Au4 tetrahedra,  an edgeedge with one Al(4)Au4 tetrahedra, edges with two equivalent Al(1)Th2Au4 tetrahedra, and faces with four equivalent Al(2)Th2Au4 tetrahedra. In the second Al site, Al(2) is bonded to two equivalent Th(1), two equivalent Au(1), and two equivalent Au(3) atoms to form AlTh2Au4 tetrahedra that share corners with two equivalent Al(3)Au4 tetrahedra, corners with two equivalent Al(2)Th2Au4 tetrahedra, corners with four equivalent Al(4)Au4 tetrahedra,  an edgeedge with one Al(3)Au4 tetrahedra, edges with two equivalent Al(2)Th2Au4 tetrahedra, and faces with four equivalent Al(1)Th2Au4 tetrahedra. In the third Al site, Al(3) is bonded to two equivalent Au(2) and two equivalent Au(3) atoms to form AlAu4 tetrahedra that share corners with two equivalent Al(2)Th2Au4 tetrahedra, corners with four equivalent Al(4)Au4 tetrahedra, corners with four equivalent Al(1)Th2Au4 tetrahedra, corners with six equivalent Al(3)Au4 tetrahedra,  an edgeedge with one Al(3)Au4 tetrahedra,  an edgeedge with one Al(2)Th2Au4 tetrahedra, and edges with four equivalent Al(4)Au4 tetrahedra. In the fourth Al site, Al(4) is bonded to two equivalent Au(2) and two equivalent Au(3) atoms to form AlAu4 tetrahedra that share corners with two equivalent Al(1)Th2Au4 tetrahedra, corners with four equivalent Al(3)Au4 tetrahedra, corners with four equivalent Al(2)Th2Au4 tetrahedra, corners with six equivalent Al(4)Au4 tetrahedra,  an edgeedge with one Al(4)Au4 tetrahedra,  an edgeedge with one Al(1)Th2Au4 tetrahedra, and edges with four equivalent Al(3)Au4 tetrahedra. Si(1) is bonded in a distorted single-bond geometry to six equivalent Th(1) and one Au(1) atom.
Th2Au5Al8Si2 crystallizes in the orthorhombic Cmmm space group. Th(1) is bonded in a 14-coordinate geometry to four equivalent Au(1), two equivalent Al(1), two equivalent Al(2), and six equivalent Si(1) atoms. All Th(1)-Au(1) bond lengths are 3.30 Å. Both Th(1)-Al(1) bond lengths are 3.48 Å. Both Th(1)-Al(2) bond lengths are 3.48 Å. There are two shorter (3.14 Å) and four longer (3.26 Å) Th(1)-Si(1) bond lengths. There are three inequivalent Au sites. In the first Au site, Au(1) is bonded in a 9-coordinate geometry to four equivalent Th(1), two equivalent Al(1), two equivalent Al(2), and one Si(1) atom. Both Au(1)-Al(1) bond lengths are 2.59 Å. Both Au(1)-Al(2) bond lengths are 2.59 Å. The Au(1)-Si(1) bond length is 2.46 Å. In the second Au site, Au(2) is bonded in a body-centered cubic geometry to four equivalent Al(3) and four equivalent Al(4) atoms. All Au(2)-Al(3) bond lengths are 2.62 Å. All Au(2)-Al(4) bond lengths are 2.62 Å. In the third Au site, Au(3) is bonded in a body-centered cubic geometry to two equivalent Al(1), two equivalent Al(2), two equivalent Al(3), and two equivalent Al(4) atoms. Both Au(3)-Al(1) bond lengths are 2.61 Å. Both Au(3)-Al(2) bond lengths are 2.61 Å. Both Au(3)-Al(3) bond lengths are 2.62 Å. Both Au(3)-Al(4) bond lengths are 2.61 Å. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to two equivalent Th(1), two equivalent Au(1), and two equivalent Au(3) atoms to form AlTh2Au4 tetrahedra that share corners with two equivalent Al(4)Au4 tetrahedra, corners with two equivalent Al(1)Th2Au4 tetrahedra, corners with four equivalent Al(3)Au4 tetrahedra,  an edgeedge with one Al(4)Au4 tetrahedra, edges with two equivalent Al(1)Th2Au4 tetrahedra, and faces with four equivalent Al(2)Th2Au4 tetrahedra. In the second Al site, Al(2) is bonded to two equivalent Th(1), two equivalent Au(1), and two equivalent Au(3) atoms to form AlTh2Au4 tetrahedra that share corners with two equivalent Al(3)Au4 tetrahedra, corners with two equivalent Al(2)Th2Au4 tetrahedra, corners with four equivalent Al(4)Au4 tetrahedra,  an edgeedge with one Al(3)Au4 tetrahedra, edges with two equivalent Al(2)Th2Au4 tetrahedra, and faces with four equivalent Al(1)Th2Au4 tetrahedra. In the third Al site, Al(3) is bonded to two equivalent Au(2) and two equivalent Au(3) atoms to form AlAu4 tetrahedra that share corners with two equivalent Al(2)Th2Au4 tetrahedra, corners with four equivalent Al(4)Au4 tetrahedra, corners with four equivalent Al(1)Th2Au4 tetrahedra, corners with six equivalent Al(3)Au4 tetrahedra,  an edgeedge with one Al(3)Au4 tetrahedra,  an edgeedge with one Al(2)Th2Au4 tetrahedra, and edges with four equivalent Al(4)Au4 tetrahedra. In the fourth Al site, Al(4) is bonded to two equivalent Au(2) and two equivalent Au(3) atoms to form AlAu4 tetrahedra that share corners with two equivalent Al(1)Th2Au4 tetrahedra, corners with four equivalent Al(3)Au4 tetrahedra, corners with four equivalent Al(2)Th2Au4 tetrahedra, corners with six equivalent Al(4)Au4 tetrahedra,  an edgeedge with one Al(4)Au4 tetrahedra,  an edgeedge with one Al(1)Th2Au4 tetrahedra, and edges with four equivalent Al(3)Au4 tetrahedra. Si(1) is bonded in a distorted single-bond geometry to six equivalent Th(1) and one Au(1) atom.