Phase formation in the BaF2–NdF3 and BaF2–PrF3 systems was studied by solid‐phase annealing at 750°С and syntheses in molten NaNO3 flux at 500°С. We observed the formation of Ba1−хRхF2+х fluorite solid solutions in the aforementioned systems, and these solid solutions underwent ordering to form ordered Ba4Nd3F17 and Ba4Pr3F17 fluorite‐like phases at 917°С and 880°С, respectively.