SmMnSi2 crystallizes in the orthorhombic Cmcm space group. Sm(1) is bonded in a 14-coordinate geometry to four equivalent Mn(1), four equivalent Si(1), and six equivalent Si(2) atoms. Mn(1) is bonded to four equivalent Sm(1) and four equivalent Si(1) atoms to form a mixture of face and edge-sharing MnSm4Si4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to four equivalent Sm(1), four equivalent Mn(1), and one Si(2) atom. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to six equivalent Sm(1), one Si(1), and two equivalent Si(2) atoms.
SmMnSi2 crystallizes in the orthorhombic Cmcm space group. Sm(1) is bonded in a 14-coordinate geometry to four equivalent Mn(1), four equivalent Si(1), and six equivalent Si(2) atoms. There are two shorter (3.29 Å) and two longer (3.30 Å) Sm(1)-Mn(1) bond lengths. All Sm(1)-Si(1) bond lengths are 3.10 Å. There are four shorter (3.04 Å) and two longer (3.13 Å) Sm(1)-Si(2) bond lengths. Mn(1) is bonded to four equivalent Sm(1) and four equivalent Si(1) atoms to form a mixture of face and edge-sharing MnSm4Si4 tetrahedra. There are two shorter (2.38 Å) and two longer (2.40 Å) Mn(1)-Si(1) bond lengths. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to four equivalent Sm(1), four equivalent Mn(1), and one Si(2) atom. The Si(1)-Si(2) bond length is 2.44 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to six equivalent Sm(1), one Si(1), and two equivalent Si(2) atoms. Both Si(2)-Si(2) bond lengths are 2.35 Å.