We construct an infinite series of simply transitive irreducible lattices in PGL 2 (F q ((t))) × PGL 2 (F q ((t))) by means of a quaternion algebra over F q (t). The lattices depend on an odd prime power q = p r and a parameter τ ∈ F * q , τ = 1, and are the fundamental group of a square complex with just one vertex and universal covering T q+1 × T q+1 , a product of trees with constant valency q + 1.Our lattices give rise via non-archimedian uniformization to smooth projective surfaces of general type over F q ((t)) with ample canonical class, Chern ratio c 2 1 / c 2 = 2, trivial Albanese variety and non-reduced Picard scheme. For q = 3, the Zariski-Euler characteristic attains its minimal value χ = 1: the surface is a non-classical fake quadric.