U3CeAl8 is Hexagonal Laves-derived structured and crystallizes in the trigonal R3m space group. There are three inequivalent U sites. In the first U site, U(1) is bonded in a 16-coordinate geometry to one U(3), three equivalent U(2), three equivalent Al(1), three equivalent Al(4), and six equivalent Al(2) atoms. In the second U site, U(2) is bonded in a 16-coordinate geometry to three equivalent U(1), one Ce(1), three equivalent Al(2), three equivalent Al(4), and six equivalent Al(1) atoms. In the third U site, U(3) is bonded in a 16-coordinate geometry to one U(1), three equivalent Ce(1), three equivalent Al(1), three equivalent Al(3), and six equivalent Al(2) atoms. Ce(1) is bonded in a 16-coordinate geometry to one U(2), three equivalent U(3), three equivalent Al(2), three equivalent Al(3), and six equivalent Al(1) atoms. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one U(1), one U(3), two equivalent U(2), two equivalent Ce(1), one Al(3), one Al(4), and four equivalent Al(1) atoms to form AlCe2U4Al6 cuboctahedra that share corners with two equivalent Al(3)Ce3U3Al6 cuboctahedra, corners with two equivalent Al(4)U6Al6 cuboctahedra, corners with four equivalent Al(1)Ce2U4Al6 cuboctahedra, corners with ten equivalent Al(2)CeU5Al6 cuboctahedra, edges with two equivalent Al(1)Ce2U4Al6 cuboctahedra, edges with four equivalent Al(2)CeU5Al6 cuboctahedra, faces with three equivalent Al(3)Ce3U3Al6 cuboctahedra, faces with three equivalent Al(4)U6Al6 cuboctahedra, faces with four equivalent Al(2)CeU5Al6 cuboctahedra, and faces with eight equivalent Al(1)Ce2U4Al6 cuboctahedra. In the second Al site, Al(2) is bonded to one U(2), two equivalent U(1), two equivalent U(3), one Ce(1), one Al(3), one Al(4), and four equivalent Al(2) atoms to form AlCeU5Al6 cuboctahedra that share corners with two equivalent Al(3)Ce3U3Al6 cuboctahedra, corners with two equivalent Al(4)U6Al6 cuboctahedra, corners with four equivalent Al(2)CeU5Al6 cuboctahedra, corners with ten equivalent Al(1)Ce2U4Al6 cuboctahedra, edges with two equivalent Al(2)CeU5Al6 cuboctahedra, edges with four equivalent Al(1)Ce2U4Al6 cuboctahedra, faces with three equivalent Al(3)Ce3U3Al6 cuboctahedra, faces with three equivalent Al(4)U6Al6 cuboctahedra, faces with four equivalent Al(1)Ce2U4Al6 cuboctahedra, and faces with eight equivalent Al(2)CeU5Al6 cuboctahedra. In the third Al site, Al(3) is bonded to three equivalent U(3), three equivalent Ce(1), three equivalent Al(1), and three equivalent Al(2) atoms to form AlCe3U3Al6 cuboctahedra that share corners with six equivalent Al(1)Ce2U4Al6 cuboctahedra, corners with six equivalent Al(2)CeU5Al6 cuboctahedra, corners with six equivalent Al(4)U6Al6 cuboctahedra, edges with six equivalent Al(3)Ce3U3Al6 cuboctahedra, faces with nine equivalent Al(1)Ce2U4Al6 cuboctahedra, and faces with nine equivalent Al(2)CeU5Al6 cuboctahedra. In the fourth Al site, Al(4) is bonded to three equivalent U(1), three equivalent U(2), three equivalent Al(1), and three equivalent Al(2) atoms to form AlU6Al6 cuboctahedra that share corners with six equivalent Al(1)Ce2U4Al6 cuboctahedra, corners with six equivalent Al(3)Ce3U3Al6 cuboctahedra, corners with six equivalent Al(2)CeU5Al6 cuboctahedra, edges with six equivalent Al(4)U6Al6 cuboctahedra, faces with nine equivalent Al(1)Ce2U4Al6 cuboctahedra, and faces with nine equivalent Al(2)CeU5Al6 cuboctahedra.
U3CeAl8 is Hexagonal Laves-derived structured and crystallizes in the trigonal R3m space group. There are three inequivalent U sites. In the first U site, U(1) is bonded in a 16-coordinate geometry to one U(3), three equivalent U(2), three equivalent Al(1), three equivalent Al(4), and six equivalent Al(2) atoms. The U(1)-U(3) bond length is 3.24 Å. All U(1)-U(2) bond lengths are 3.36 Å. All U(1)-Al(1) bond lengths are 3.24 Å. All U(1)-Al(4) bond lengths are 3.24 Å. All U(1)-Al(2) bond lengths are 3.20 Å. In the second U site, U(2) is bonded in a 16-coordinate geometry to three equivalent U(1), one Ce(1), three equivalent Al(2), three equivalent Al(4), and six equivalent Al(1) atoms. The U(2)-Ce(1) bond length is 3.47 Å. All U(2)-Al(2) bond lengths are 3.14 Å. All U(2)-Al(4) bond lengths are 3.22 Å. All U(2)-Al(1) bond lengths are 3.26 Å. In the third U site, U(3) is bonded in a 16-coordinate geometry to one U(1), three equivalent Ce(1), three equivalent Al(1), three equivalent Al(3), and six equivalent Al(2) atoms. All U(3)-Ce(1) bond lengths are 3.40 Å. All U(3)-Al(1) bond lengths are 3.33 Å. All U(3)-Al(3) bond lengths are 3.25 Å. All U(3)-Al(2) bond lengths are 3.19 Å. Ce(1) is bonded in a 16-coordinate geometry to one U(2), three equivalent U(3), three equivalent Al(2), three equivalent Al(3), and six equivalent Al(1) atoms. All Ce(1)-Al(2) bond lengths are 3.22 Å. All Ce(1)-Al(3) bond lengths are 3.23 Å. All Ce(1)-Al(1) bond lengths are 3.25 Å. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one U(1), one U(3), two equivalent U(2), two equivalent Ce(1), one Al(3), one Al(4), and four equivalent Al(1) atoms to form AlCe2U4Al6 cuboctahedra that share corners with two equivalent Al(3)Ce3U3Al6 cuboctahedra, corners with two equivalent Al(4)U6Al6 cuboctahedra, corners with four equivalent Al(1)Ce2U4Al6 cuboctahedra, corners with ten equivalent Al(2)CeU5Al6 cuboctahedra, edges with two equivalent Al(1)Ce2U4Al6 cuboctahedra, edges with four equivalent Al(2)CeU5Al6 cuboctahedra, faces with three equivalent Al(3)Ce3U3Al6 cuboctahedra, faces with three equivalent Al(4)U6Al6 cuboctahedra, faces with four equivalent Al(2)CeU5Al6 cuboctahedra, and faces with eight equivalent Al(1)Ce2U4Al6 cuboctahedra. The Al(1)-Al(3) bond length is 2.78 Å. The Al(1)-Al(4) bond length is 2.74 Å. There are two shorter (2.75 Å) and two longer (2.76 Å) Al(1)-Al(1) bond lengths. In the second Al site, Al(2) is bonded to one U(2), two equivalent U(1), two equivalent U(3), one Ce(1), one Al(3), one Al(4), and four equivalent Al(2) atoms to form AlCeU5Al6 cuboctahedra that share corners with two equivalent Al(3)Ce3U3Al6 cuboctahedra, corners with two equivalent Al(4)U6Al6 cuboctahedra, corners with four equivalent Al(2)CeU5Al6 cuboctahedra, corners with ten equivalent Al(1)Ce2U4Al6 cuboctahedra, edges with two equivalent Al(2)CeU5Al6 cuboctahedra, edges with four equivalent Al(1)Ce2U4Al6 cuboctahedra, faces with three equivalent Al(3)Ce3U3Al6 cuboctahedra, faces with three equivalent Al(4)U6Al6 cuboctahedra, faces with four equivalent Al(1)Ce2U4Al6 cuboctahedra, and faces with eight equivalent Al(2)CeU5Al6 cuboctahedra. The Al(2)-Al(3) bond length is 2.76 Å. The Al(2)-Al(4) bond length is 2.74 Å. There are two shorter (2.75 Å) and two longer (2.76 Å) Al(2)-Al(2) bond lengths. In the third Al site, Al(3) is bonded to three equivalent U(3), three equivalent Ce(1), three equivalent Al(1), and three equivalent Al(2) atoms to form AlCe3U3Al6 cuboctahedra that share corners with six equivalent Al(1)Ce2U4Al6 cuboctahedra, corners with six equivalent Al(2)CeU5Al6 cuboctahedra, corners with six equivalent Al(4)U6Al6 cuboctahedra, edges with six equivalent Al(3)Ce3U3Al6 cuboctahedra, faces with nine equivalent Al(1)Ce2U4Al6 cuboctahedra, and faces with nine equivalent Al(2)CeU5Al6 cuboctahedra. In the fourth Al site, Al(4) is bonded to three equivalent U(1), three equivalent U(2), three equivalent Al(1), and three equivalent Al(2) atoms to form AlU6Al6 cuboctahedra that share corners with six equivalent Al(1)Ce2U4Al6 cuboctahedra, corners with six equivalent Al(3)Ce3U3Al6 cuboctahedra, corners with six equivalent Al(2)CeU5Al6 cuboctahedra, edges with six equivalent Al(4)U6Al6 cuboctahedra, faces with nine equivalent Al(1)Ce2U4Al6 cuboctahedra, and faces with nine equivalent Al(2)CeU5Al6 cuboctahedra.