New integrable model of correlated electrons with off-diagonal   long-range order from $so(5)$ symmetry
  We present a new integrable model for correlated electrons which is based on a $so(5)$ symmetry. By using an $\eta$-pairing realization we construct eigenstates of the Hamiltonian with off-diagonal long-range order. It is also shown that these states lie in the ground state sector. We exactly solve the model on a one-dimensional lattice by the Bethe ansatz. 
Angela Foerster, Jon Links and Itzhak Roditi