  The generalization of Lorentz invariance to solvable two-dimensional lattice
fermion models has been formulated in terms of Baxter's corner transfer matrix.
In these models, the lattice Hamiltonian and boost operator are given by
fermionized nearest-neighbor Heisenberg spin chain operators. The
transformation properties of the local lattice fermion operators under a boost
provide a natural and precise way of generalizing the chiral structure of a
continuum Dirac field to the lattice. The resulting formulation differs from
both the Wilson and staggered (Kogut-Susskind) prescriptions. In particular, an
axial $Q_5$ rotation is sitewise local, while the vector charge rotation mixes
nearest neighbors on even and odd sublattices.
