  Stellar kinematics and metallicity are key to exploring formation scenarios
for galactic disks and halos. In this work, we characterized the relationship
between kinematics and photometric metallicity along the line-of-sight to M31's
disk. We combined optical HST/ACS photometry from the Panchromatic Hubble
Andromeda Treasury (PHAT) survey with Keck/DEIMOS spectra from the
Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo (SPLASH)
survey. The resulting sample of 3512 individual red giant branch stars spans
4-19 projected kpc, making it a useful probe of both the disk and inner halo.
We separated these stars into disk and halo populations by modeling the
line-of-sight velocity distributions as a function of position across the disk
region, where $\sim$73% stars have a high likelihood of belonging to the disk
and $\sim$14% to the halo. Although stellar halos are typically thought to be
metal-poor, the kinematically identified halo contains a significant population
of stars ($\sim$29%) with disk-like metallicity ([Fe/H]$_{\rm phot}$ $\sim$
$-0.10$). This metal-rich halo population lags the gaseous disk to a similar
extent as the rest of the halo, indicating that it does not correspond to a
canonical thick disk. Its properties are inconsistent with those of tidal
debris originating from the Giant Stellar Stream merger event. Moreover, the
halo is chemically distinct from the phase-mixed component previously
identified along the minor axis (i.e., away from the disk), implying
contributions from different formation channels. These metal-rich halo stars
provide direct chemodynamical evidence in favor of the previously suggested
"kicked-up" disk population in M31's inner stellar halo.

Astrophysics of Galaxies