  We investigate the magnetic excitations of the hyperhoneycomb Kitaev magnet
$\beta$-$\text{Li}_2\text{IrO}_3$ by means of inelastic Raman scattering. The
spectra exhibits a coexistence of a broad scattering continuum and two sharp
low-energy peaks at 2.5 meV and 3 meV, with a distinctive polarization
dependence. While the continuum is suggestive of fractional quasi-particles
emerging from a proximate quantum spin liquid phase, the sharp peaks provide
the first experimental signature of the `non-Loudon-Fleury' one-magnon
scattering processes proposed recently [Phys. Rev. B 104, 144412 (2021)]. The
corresponding microscopic mechanism is similar to the one leading to the
symmetric off-diagonal exchange interaction $\Gamma$ (as it involves a
combination of both direct and ligand-mediated exchange paths), but is
otherwise completely unexpected within the traditional Loudon-Fleury theory of
Raman scattering. The present experimental verification therefore calls for a
drastic reevaluation of Raman scattering in similar systems with strong spin
orbit coupling and multiple exchange paths.
