  We consider the analogue of the 6-vertex model constructed from alternating
spin n/2 and spin m/2 lines, where $1\leq n<m$. We identify the transfer matrix
and the space on which it acts in terms of the representation theory of
$U_q(sl_2)$. We diagonalise the transfer matrix and compute the S-matrix. We
give a trace formula for local correlation functions. When n=1, the 1-point
function of a spin m/2 local variable for the alternating lattice with a
particular ground state is given as a linear combination of the 1-point
functions of the pure spin m/2 model with different ground states. The mixing
ratios are calculated exactly and are expressed in terms of irreducible
characters of $U_q(sl_2)$ and the deformed Virasoro algebra.
