Factorization identities and algebraic Bethe ansatz for $D_2^{(2)}$ models

We express $D_2^{(2)}$ transfer matrices as products of $A_1^{(1)}$ transfer matrices, for both closed and open spin chains. We use these relations, which we call factorization identities, to solve the models by algebraic Bethe ansatz. We also formulate and solve a new integrable XXZ-like open spin chain with an even number of sites that depends on a continuous parameter, which we interpret as the rapidity of the boundary.