Half-metallic Heusler alloys are gathering enormous interest as a platform for the next generation of spintronic devices, due to their unique band structure characterized by highly spin-polarized electronic transport at the Fermi level.[1, 2] Here, the broadband ferromagnetic resonance spectroscopy (FMR) is adopted to investigate on the thickness-dependent magnetization dynamic of the MnPtSb (t)/Co (5nm)/Au (5nm) heterostructure down to t= 1nm, demonstrating the possibility to use the MnPtSb alloy as an efficient spin-current generator. Spin pumping-FMR is also employed to determine the spin-to-charge conversion nature in such a system [3], indicating a predominant contribution from the surface states of the MnPtSb compound. Moreover, when interpreted as arising from the Inverse Edelstein Effect (IEE), the spin-charge conversion efficiency extracted at room temperature for the thinner samples reaches λ IEE …