  The algebraic Bethe ansatz is a powerful method to diagonalize
transfer-matrices of statistical models derived from solutions of (graded) Yang
Baxter equations, connected to fundamental representations of Lie
(super-)algebras and their quantum deformations respectively. It is, however,
very difficult to apply it to models based on higher dimensional
representations of these algebras in auxiliary space, which are not of fusion
type. A systematic approach to this problem is presented here. It is
illustrated by the diagonalization of a transfer-matrix of a model based on the
product of two different four-dimensional representations of
$U_{q}(\hat{gl}'(2,1;C))$.
