The Pristine survey XXV: The Galactic underdogs -- Dynamic tales of a Milky Way metal-poor population

Through the chemodynamical characterisation of metal-poor stars, one can efficiently probe the early history of the Milky Way. We aim at decontaminating a sample of 3M giant stars with Gaia DR3 XP-based Pristine-Gaia metallicities, to investigate a subset of very metal-poor stars (Fe/H 180 km s^-1 and Z₌₀ₗ < 1. 5 kpc, down to Fe/H = -2. 9 at a 2 confidence level. While the overall orbital distributions of our sample match that of a halo, the highly prograde and planar subset (2% of the very metal-poor population) also bears characteristics classically associated with a thick disc, i. e. , a spatial distribution compatible with a short-scaled thick disc, and a thick disc-like Z₌₀ₗ - R₌₀ₗ distribution. Additionally, assuming a stationary or prograde halo with V_ 30-40 km. s^-1 is not sufficient to suppress the kinematic signature of the highly prograde and planar subset. These results rule out any link with a thin disc, and instead, support a contribution from a metal-weak thick disc.