  We consider a two-parameter $(\bar c, \tilde c)$ family of quantum integrable
Hamiltonians for a chain of alternating spins of spin $s=1/2$ and $s=1$. We
determine the thermodynamics for low-temperature $T$ and small external
magnetic field $H$, with $T << H$. In the antiferromagnetic $(\bar c > 0,
\tilde c > 0)$ case, the model has two gapless excitations. In particular, for
$\bar c = \tilde c$, the model is conformally invariant and has central charge
$c_{vir} = 2$. When one of these parameters is zero, the Bethe Ansatz equations
admit an infinite number of solutions with lowest energy.
