We implement axio-dilaton fields from spin geometry and indicate potential links between these structures and conformal spacetimes. Our approach is based on the complex generalization \(\Omega \varepsilon _{AB}\) of the metric spinor \(\varepsilon _{AB}\) , which simultaneously converts Maxwell electrodynamics in vacuum into axio-dilaton electrodynamics with modular coupling \(\tilde{\tau }=\textbf{i}\Omega ^{-2}\) and the spacetime metric into a conformally related metric rescaled by \((\Omega ^{*}\Omega )\) . By applying this complex rescaling to the Maxwell-Euler-Heisenberg theory, we demonstrate that this approach not only reproduces established axio-dilaton structures in the linear regime but also uncovers new mathematical structures within the nonlinear sector. Subsequently, by focusing on the duality group of \(\tilde{\tau }\) , a set of SL \((2,\mathbb {Z})\) -dual metrics for the conformally equivalent spacetime is obtained through the Infeld-van der Waerden map. As a formal application of these dualities, we adapt our formulation to conformal cyclic cosmology and show how the pre- and post-conformal metrics can be mapped to each other via \(\mathcal {S}\) -duality.
