Neptunium(III) phosphide

Neptunium(III) phosphide is a binary inorganic compound of neptunium metal and phosphorus with the chemical formula NpP.

Preparation
Neptunium(III) phosphide can be formed from the fusion of stoichiometric amounts of neptunium and phosphorus at 750 °C:
 * 4 Np + P4 -> 4 NpP

Physical properties
Neptunium(III) phosphide forms black crystals of NaCl-structure. It is insoluble in water. It is antiferromagnetic below 130 K.