Sc3Mn3Al7Si5 crystallizes in the hexagonal P6_3/mmc space group. Sc(1) is bonded in a 11-coordinate geometry to one Al(2), six equivalent Al(1), two equivalent Si(1), and two equivalent Si(2) atoms. Mn(1) is bonded in a 8-coordinate geometry to four equivalent Al(1), two equivalent Si(1), and two equivalent Si(2) atoms. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 11-coordinate geometry to three equivalent Sc(1), two equivalent Mn(1), one Al(2), two equivalent Al(1), one Si(2), and two equivalent Si(1) atoms. In the second Al site, Al(2) is bonded in a 9-coordinate geometry to three equivalent Sc(1) and six equivalent Al(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(2) is bonded in a 9-coordinate geometry to three equivalent Sc(1), three equivalent Mn(1), and three equivalent Al(1) atoms. In the second Si site, Si(1) is bonded in a 8-coordinate geometry to two equivalent Sc(1), two equivalent Mn(1), and four equivalent Al(1) atoms.
Sc3Mn3Al7Si5 crystallizes in the hexagonal P6_3/mmc space group. Sc(1) is bonded in a 11-coordinate geometry to one Al(2), six equivalent Al(1), two equivalent Si(1), and two equivalent Si(2) atoms. The Sc(1)-Al(2) bond length is 2.87 Å. There are two shorter (2.98 Å) and four longer (3.05 Å) Sc(1)-Al(1) bond lengths. Both Sc(1)-Si(1) bond lengths are 2.83 Å. Both Sc(1)-Si(2) bond lengths are 2.69 Å. Mn(1) is bonded in a 8-coordinate geometry to four equivalent Al(1), two equivalent Si(1), and two equivalent Si(2) atoms. All Mn(1)-Al(1) bond lengths are 2.51 Å. Both Mn(1)-Si(1) bond lengths are 2.39 Å. Both Mn(1)-Si(2) bond lengths are 2.41 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 11-coordinate geometry to three equivalent Sc(1), two equivalent Mn(1), one Al(2), two equivalent Al(1), one Si(2), and two equivalent Si(1) atoms. The Al(1)-Al(2) bond length is 2.80 Å. Both Al(1)-Al(1) bond lengths are 2.75 Å. The Al(1)-Si(2) bond length is 2.64 Å. Both Al(1)-Si(1) bond lengths are 2.61 Å. In the second Al site, Al(2) is bonded in a 9-coordinate geometry to three equivalent Sc(1) and six equivalent Al(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(2) is bonded in a 9-coordinate geometry to three equivalent Sc(1), three equivalent Mn(1), and three equivalent Al(1) atoms. In the second Si site, Si(1) is bonded in a 8-coordinate geometry to two equivalent Sc(1), two equivalent Mn(1), and four equivalent Al(1) atoms.