Published online by Cambridge University Press: 20 March 2017
By means of a quaternion algebra over $\mathbb{F}$q(t), we construct an infinite series of torsion free, simply transitive, irreducible lattices in PGL2($\mathbb{F}$q((t))) × PGL2($\mathbb{F}$q((t))). The lattices depend on an odd prime power q = pr and a parameter τ ∈ $\mathbb{F}$q×, τ ≠ 1, and are the fundamental group of a square complex with just one vertex and universal covering Tq+1 × Tq+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 $\mathbb{F}$q((t)) with ample canonical class, Chern numbers c12 = 2 c2, 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.