The class of universality of integrable and isotropic GL(N) mixed magnets

We discuss a class of transfer matrix built by a particular combination of isomorphic and non-isomorphic GL(N) invariant vertex operators. We construct a conformally invariant magnet constituted of an alternating mixture of GL(N) ``spins'' operators at different order of representation. The corresponding central charge is calculated by analysing the low temperature behaviour of the associated free energy. We also comment on possible extensions of our results for more general classes of mixed systems.