  The ever-increasing demand for efficient data storage and processing has
fueled the search for novel memory devices. Spintronics offers an alternative
fast and efficient solution using spin-to-charge interconversion. In this work,
we demonstrate a remarkable thirty-four-fold increase in spin-to-charge current
conversion when incorporating a 2D epitaxial graphene monolayer between iron
and platinum layers by exploring spin-pumping on-chip devices. Furthermore, we
find that the spin conversion is also anisotropic. We attribute this
enhancement and anisotropy to the asymmetric Rashba contributions driven by an
unbalanced spin accumulation at the differently hybridized top and bottom
graphene interfaces, as highlighted by ad-hoc first-principles theory. The
improvement in spin-to-charge conversion as well as its anisotropy reveals the
importance of interfaces in hybrid 2D-thin film systems opening up new
possibilities for engineering spin conversion in 2D materials, leading to
potential advances in memory, logic applications, or unconventional computing.
