We show that every generalized quadrangle of order \((4,6)\) with a spread of symmetry is isomorphic to the Ahrens-Szekeres generalized quadrangle \(\text{AS}(5)\). It then easily follows that every generalized quadrangle of order \(5\) with an axis of symmetry is isomorphic to the classical generalized quadrangle \(\text{Q}(4, 5)\).
Citation
Bart De Bruyn. The Uniqueness of the Generalized Quadrangle of Order \(5\) with an Axis of Symmetry[J], Ars Combinatoria, Volume 088. 203-216. .