Quantum L-operator of the critical Ising model

We consider the two-dimensional Ising model on the square lattice at the critical temperature. This model can be related to the free-fermion eight-vertex model with the trigonometric dependence of the Boltzmann weights on the spectral variable. We obtain the quantum L-operator as a solution of the RLL-relation assuming the spectral variable dependence similar to that of the R-matrix.