Fe3IrSi4 crystallizes in the trigonal R3 space group. Fe(1) is bonded in a 9-coordinate geometry to two equivalent Ir(1), two equivalent Si(1), and five equivalent Si(2) atoms. Ir(1) is bonded in a 13-coordinate geometry to six equivalent Fe(1), one Si(1), and six equivalent Si(2) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to six equivalent Fe(1) and one Ir(1) atom. In the second Si site, Si(2) is bonded in a 7-coordinate geometry to five equivalent Fe(1) and two equivalent Ir(1) atoms.
Fe3IrSi4 crystallizes in the trigonal R3 space group. Fe(1) is bonded in a 9-coordinate geometry to two equivalent Ir(1), two equivalent Si(1), and five equivalent Si(2) atoms. There is one shorter (2.79 Å) and one longer (2.80 Å) Fe(1)-Ir(1) bond length. There is one shorter (2.29 Å) and one longer (2.60 Å) Fe(1)-Si(1) bond length. There are a spread of Fe(1)-Si(2) bond distances ranging from 2.29-2.59 Å. Ir(1) is bonded in a 13-coordinate geometry to six equivalent Fe(1), one Si(1), and six equivalent Si(2) atoms. The Ir(1)-Si(1) bond length is 2.40 Å. There are three shorter (2.40 Å) and three longer (2.59 Å) Ir(1)-Si(2) bond lengths. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to six equivalent Fe(1) and one Ir(1) atom. In the second Si site, Si(2) is bonded in a 7-coordinate geometry to five equivalent Fe(1) and two equivalent Ir(1) atoms.