  Using data from the Gaia satellite's Radial Velocity Spectrometer Data
Release 3 (RVS, DR3), we find a new and robust feature in the phase space
distribution of halo stars. It is a prominent ridge at constant energy and with
angular momentum $L_z>0$. We run test particle simulations of a stellar
halo-like distribution of particles in a realistic Milky Way potential with a
rotating bar. We observe similar structures generated in the simulations from
the trapping of particles in resonances with the bar, particularly at the
corotation resonance. Many of the orbits trapped at the resonances are
halo-like, with large vertical excursions from the disc. The location of the
observed structure in energy space is consistent with a bar pattern speed in
the range $\Omega_\mathrm{b}\approx35-40$ km s$^{-1}$ kpc$^{-1}$. Overall, the
effect of the resonances is to give the inner stellar halo a mild, net spin in
the direction of the bar's rotation. As the distribution of the angular
momentum becomes asymmetric, a population of stars with positive mean $L_z$ and
low vertical action is created. The variation of the average rotational
velocity of the simulated stellar halo with radius is similar to the behaviour
of metal-poor stars in data from the APOGEE survey. Though the effects of bar
resonances have long been known in the Galactic disc, this is strong evidence
that the bar can drive changes even in the diffuse and extended stellar halo
through its resonances.
