It is a narrow-bandgap semiconductor with a room-temperature electrical resistivity of around 10 kΩ·cm[3] and unusual magnetic properties at low temperatures.

FeSi has a cubic crystal lattice with no inversion center; therefore its magnetic structure is helical, with right-hand and left-handed chiralities.

Whereas in sodium chloride the eight atoms are at the corners of a cube and each ion is surrounded by six counterions, in iron monosilicide the atoms are all displaced parallel to body diagonals (along threefold axes) from the positions of sodium and chloride.

(Threefold screw axes also exist in sodium chloride but are related by a mirror.)

This means that iron monosilicide crystals exist in two different enantiomorphs, depending on the signs of x and y.