  We present the metallicities and carbon abundances of four newly discovered
metal-poor stars with $ -2.2 <$ [Fe/H] $< -1.6$ in the Sagittarius dwarf
spheroidal galaxy. These stars were selected as metal-poor member candidates
using a combination of public photometry from the SkyMapper Southern Sky Survey
and proper motion data from the second data release from the Gaia mission. The
SkyMapper filters include a metallicity-sensitive narrow-band $v$ filter
centered on the Ca II K line, which we use to identify metal-poor candidates.
In tandem, we use proper motion data to remove metal-poor stars that are not
velocity members of the Sagittarius dwarf spheroidal galaxy. We find that these
two datasets allow for efficient identification of metal-poor members of the
Sagittarius dwarf galaxy to follow-up with further spectroscopic study. Two of
the stars we present have [Fe/H] $< -2.0$, which adds to the few other such
stars currently identified in the Sagittarius dwarf galaxy that are likely not
associated with the globular cluster M54, which resides in the nucleus of the
system. Our results confirm that there exists a very metal-poor stellar
population in the Sagittarius dwarf galaxy. We find that none of our stars can
be classified as carbon-enhanced metal-poor stars. Efficiently identifying
members of this population will be helpful to further our understanding of the
early chemical evolution of the system.
