Abstract
We extend a lemma by Matsuda about the irreducibility of the
binomial X 1 in the semigroup ring F[X;G], where F is a eld, G is an
abelian torsion-free group and is an element of G of height (0; 0; 0; : : : ).
In our extension, G is replaced by any submonoid of (Q+; +). The eld F,
however, has to be of characteristic 0. We give an application of our main
result.