Some Questions on the Ideal Class Group of Imaginary Abelian Fields

Let k be an imaginary quadratic field. Assume that the class number of k is exactly an odd prime number p, and p splits into two distinct primes in k. Then it is known that a prime ideal lying above p is not principal. In the present paper, we shall consider a question whether a similar result holds when the class number of k is 2p. We also consider an analogous question for the case that k is an imaginary quartic abelian field.