Spin-orbitronics, which exploits the coupling between the spin and the orbital momentum of electrons, relies on the possibility to electrically create and detect pure spin currents without need of ferromagnetic elements. An efficient way to achieve this spin-to-charge conversion (and vice versa) is expected by exploiting the Rashba-Edelstein effect. This phenomenon is related to the well-known spin Hall effect, but in the former, the spin-to-charge current conversion occurs at the interface of materials with a strong spin splitting of the surface states, instead of the bulk. This paper reports an observation of the inverse Rashba-Edelstein effect, i.e., conversion of a spin current into a charge current, at a bismuth/copper interface, by using spin absorption with lateral spin valves. The induced charge current changes sign with temperature, a phenomenon that the authors can explain theoretically owing to the complex spin structure and dispersion of the surface states at the Fermi energy.