AgNi3(PO4)(HPO4)2: an alluaudite‐like structure

The new title phosphate, silver trinickel phosphate bis(hydrogenphosphate), has been synthesized by the hydro­thermal method. It has an alluaudite‐like structure but shows some differences owing to the presence of the H atoms. The structure is isomorphous with the compounds of general formula AM₃(XO₄)(HXO₄)₂ (A is Na or Ag, M is Co, Zn or Mn, and X is As or P), with the Ag atom, one Ni atom and one P atom lying on twofold axes.