Neptunium silicide is a binary inorganic compound of neptunium and silicon with the chemical formula . The compound forms crystals and does not dissolve in water.
Heating neptunium trifluoride with powdered silicon in vacuum:
Neptunium silicide forms crystals of tetragonal crystal system, space group I4<sub>1</sub>/amd, cell parameters: a = 0.396 nm, c = 1.367 nm, Z = 4.
Neptunium disilicide does not dissolve in water.
Neptunium disilicide reacts with HCl: