  Spin-to-charge current interconversions are widely exploited for the
generation and detection of pure spin currents and are key ingredients for
future spintronic devices including spin-orbit torques and spin-orbit logic
circuits. In case of the spin Hall effect, different mechanisms contribute to
the phenomenon and determining the leading contribution is peremptory for
achieving the largest conversion efficiencies. Here, we experimentally
demonstrate the dominance of the intrinsic mechanism of the spin Hall effect in
highly-resistive Ta. We obtain an intrinsic spin Hall conductivity for
$\beta$-Ta of -820$\pm$120 ($\hbar$/e) $\Omega^{-1}cm^{-1}$ from spin
absorption experiments in a large set of lateral spin valve devices. The
predominance of the intrinsic mechanism in Ta allows us to linearly enhance the
spin Hall angle by tuning the resistivity of Ta, reaching up to -35$\pm$3%, the
largest reported value for a pure metal.
