PrS
Zhuravlev, N.N.Stepanova, A.A.Shebatinov, M.P.
Soviet Physics, Crystallography (= Kristallografiya) (1964) 9, 95-96
a=5.763Å b=5.763Å c=5.763Å
α=90° β=90° γ=90°
NdS
a=5.715Å b=5.715Å c=5.715Å