  Modern astrometric and spectroscopic surveys have revealed a wealth of
structure in the phase space of stars in the Milky Way, with evidence of
resonance features and non-equilibrium processes. Using Gaia's third data
release, we present evidence of a new resonance-like feature in the outer disc
of the Milky Way. The feature is most evident in the angular momentum
distribution of the young Classical Cepheids, a population for which we can
derive accurate distances over much of the Galactic disc. We then search for
similar features in the outer disc using a much larger sample of red giant
stars, as well as a compiled list of over 31 million stars with spectroscopic
line-of-sight velocity measurements. While much less evident in these two older
samples, the distribution of stars in action-configuration space suggests that
resonance features are present here as well. The position of the feature in
action-configuration space suggests that the new feature may be related to the
Galactic bar, but other possibilities are discussed.
