  We show that any Lambda-ring, in the sense of Riemann-Roch theory, which is
finite etale over the rational numbers and has an integral model as a
Lambda-ring is contained in a product of cyclotomic fields. In fact, we show
that the category of them is described in a Galois-theoretic way in terms of
the monoid of pro-finite integers under multiplication and the cyclotomic
character. We also study the maximality of these integral models and give a
more precise, integral version of the result above. These results reveal an
interesting relation between Lambda-rings and class field theory.
