The Quantum Algebraic Structure of the Twisted XXZ Chain
  We consider the Quantum Inverse Scattering Method with a new R-matrix depending on two parameters $q$ and $t$. We find that the underlying algebraic structure is the two-parameter deformed algebra $SU_{q,t}(2)$ enlarged by introducing an element belonging to the centre. The corresponding Hamiltonian describes the spin-1/2 XXZ model with twisted periodic boundary conditions. 
M.R-Monteiro, I.Roditi, L.M.C.S.Rodrigues and S.Sciuto