The exact solution and the finite size behaviour of the Osp(1|2) invariant spin chain

We have solved exactly the $Osp(1|2)$ spin chain by the Bethe ansatz approach. Our solution is based on an equivalence between the $Osp(1|2)$ chain and certain special limit of the Izergin-Korepin vertex model. The completeness of the Bethe ansatz equations is discussed for a system with four sites and it is noted the appearance of special string structures. The Bethe ansatz presents an important phase-factor which distinguishes the even and odd sectors of the theory. The finite size properties are governed by a conformal field theory with central charge $c=1$.