Replacing noble metal catalysts with inexpensive substitutes is a big challenge for the chemical industry. Several complex Al-based intermetallic compounds have already been identified as promising catalysts for hydrogenation reactions [1,2]. The understanding of the underlying processes requires a precise determination of the surface structure, as well as (i) the thermodynamic quantities related to the adsorption of molecules involved in the reaction and (ii) the energy barriers of the elemental processes. In this work, a precise surface model for Al5Co2 is deduced from a combination of calculations based on the Density Functional Theory (DFT) and surface sciences techniques [3], including Surface X-Ray Diffraction experiments (Synchrotron SOLEIL). A thermodymamic model is built, powered by theoretical adsorption energies, in order to take into account the reaction conditions (pressure and temperature). The calculated favorable reaction conditions are then compared to the experimental conditions. This work illustrates the complementarity of experimental and theoretical approaches for the understanding of the reactivity of complex intermetallic surfaces. It also paves the way to investigations of more complex systems, like the quasicrystalline approximants Al13TM4. [1] M. Armbrüster et al., Nat. Mater., 2012, 11, 690–693. [2] L. Piccolo, Chem. Commun., 2013, 49, 9149 [3] M. Meier et al., Phys. Rev. B 93, 075412 (2016)