  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 co nstituted of an alternating mixture of GL(N)
``spins'' operators at different order of represent ation. The corresponding
central charge is calculated by analysing the low temperature beha viour of the
associated free energy. We also comment on possible extensions of our results
for more general classes of mixed systems.
