Four-dimensional semi-Riemannian Szab\'o manifolds
In this paper, we prove that the deformed Riemannian extension of any affine Szab\'o manifold is a Szab\'o pseudo-Riemannian metric and vice-versa. We proved that the Ricci tensor of an affine surface is skew-symmetric and nonzero everywhere if and only if the affine surface is Szab\'o. We also find the necessary and sufficient condition for the affine Szab\'o surface to be recurrent. We prove that for an affine Szab\'o recurrent surface the recurrence covector of a recurrence tensor is not locally a gradient.