Nb2Mn4Si5 crystallizes in the orthorhombic Ibam space group. Nb(1) is bonded in a 6-coordinate geometry to two equivalent Si(1) and four equivalent Si(2) atoms. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 7-coordinate geometry to one Si(1), two equivalent Si(3), and four equivalent Si(2) atoms. In the second Mn site, Mn(2) is bonded in a 7-coordinate geometry to one Si(2), two equivalent Si(3), and four equivalent Si(1) atoms. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to two equivalent Nb(1), one Mn(1), four equivalent Mn(2), and one Si(1) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to four equivalent Nb(1), one Mn(2), and four equivalent Mn(1) atoms. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to four equivalent Mn(1), four equivalent Mn(2), and two equivalent Si(3) atoms.
Nb2Mn4Si5 crystallizes in the orthorhombic Ibam space group. Nb(1) is bonded in a 6-coordinate geometry to two equivalent Si(1) and four equivalent Si(2) atoms. Both Nb(1)-Si(1) bond lengths are 2.60 Å. There are two shorter (2.61 Å) and two longer (2.62 Å) Nb(1)-Si(2) bond lengths. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 7-coordinate geometry to one Si(1), two equivalent Si(3), and four equivalent Si(2) atoms. The Mn(1)-Si(1) bond length is 2.52 Å. Both Mn(1)-Si(3) bond lengths are 2.90 Å. There are a spread of Mn(1)-Si(2) bond distances ranging from 2.46-2.83 Å. In the second Mn site, Mn(2) is bonded in a 7-coordinate geometry to one Si(2), two equivalent Si(3), and four equivalent Si(1) atoms. The Mn(2)-Si(2) bond length is 2.38 Å. Both Mn(2)-Si(3) bond lengths are 2.47 Å. There are a spread of Mn(2)-Si(1) bond distances ranging from 2.31-2.79 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 8-coordinate geometry to two equivalent Nb(1), one Mn(1), four equivalent Mn(2), and one Si(1) atom. The Si(1)-Si(1) bond length is 2.42 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to four equivalent Nb(1), one Mn(2), and four equivalent Mn(1) atoms. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to four equivalent Mn(1), four equivalent Mn(2), and two equivalent Si(3) atoms. Both Si(3)-Si(3) bond lengths are 2.57 Å.