Using Monte Carlo simulations and finite-size scaling analysis, the critical behavior of attractive rigid rods of length k (k-mers) on square lattices at intermediate density has been studied. A nematic phase, characterized by a big domain of paralle
l k-mers, was found. This ordered phase is separated from the isotropic state by a continuous transition occurring at a intermediate density theta_c, which increases linearly with the magnitude of the lateral interactions.
