Let F be a finite extension
of the field of rational numbers, 𝒫 a prime ideal in the ring of algebraic integers in F,
and xm− μ irreducible over F. If m is a prime and ζm∈ F, then the ideal
decomposition of 𝒫 in F(μ1∕m) has been described by Hensel. If m = lt, l a prime
and (l,𝒫) = 1, then the decomposition of 𝒫 in F(μ1∕lt) was obtained by
Mann and Vélez, with no restriction on roots of unity. In this paper we
describe the decomposition of 𝒫 in the fields F(ζp) and F(μ1∕p), where
𝒫⊃ (p).