Al9FeMg3Si5 crystallizes in the hexagonal P-62m space group. Mg(1) is bonded in a 5-coordinate geometry to one Si(2) and four equivalent Si(1) atoms. Fe(1) is bonded in a 9-coordinate geometry to three equivalent Al(1) and six equivalent Al(2) atoms. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 5-coordinate geometry to one Fe(1) and four equivalent Si(1) atoms. In the second Al site, Al(2) is bonded in a 4-coordinate geometry to one Fe(1), one Si(2), and two equivalent Si(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to three equivalent Mg(1), three equivalent Al(1), and three equivalent Al(2) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to three equivalent Mg(1) and six equivalent Al(2) atoms.
Al9FeMg3Si5 crystallizes in the hexagonal P-62m space group. Mg(1) is bonded in a 5-coordinate geometry to one Si(2) and four equivalent Si(1) atoms. The Mg(1)-Si(2) bond length is 2.78 Å. All Mg(1)-Si(1) bond lengths are 2.87 Å. Fe(1) is bonded in a 9-coordinate geometry to three equivalent Al(1) and six equivalent Al(2) atoms. All Fe(1)-Al(1) bond lengths are 2.50 Å. All Fe(1)-Al(2) bond lengths are 2.41 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 5-coordinate geometry to one Fe(1) and four equivalent Si(1) atoms. All Al(1)-Si(1) bond lengths are 2.80 Å. In the second Al site, Al(2) is bonded in a 4-coordinate geometry to one Fe(1), one Si(2), and two equivalent Si(1) atoms. The Al(2)-Si(2) bond length is 2.74 Å. Both Al(2)-Si(1) bond lengths are 2.54 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to three equivalent Mg(1), three equivalent Al(1), and three equivalent Al(2) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to three equivalent Mg(1) and six equivalent Al(2) atoms.