  In systems with detected planets, hot-Jupiters and compact systems of
multiple planets are nearly mutually exclusive. We compare the relative
occurrence of these two architectures as a fraction of detected planetary
systems to determine the role that metallicity plays in planet formation. We
show that compact multi-planet systems occur more frequently around stars of
increasingly lower metallicities using spectroscopically derived abundances for
more than 700 planet hosts. At higher metallicities, compact multi-planet
systems comprise a nearly constant fraction of the planet hosts despite the
steep rise in the fraction of hosts containing hot and cool-Jupiters. Since
metal poor stars have been underrepresented in planet searches, this implies
that the occurrence rate of compact multis is higher than previously reported.
Due to observational limits, radial velocity planet searches have focused
mainly on high-metallicity stars where they have a higher chance of finding
giant planets. New extreme-precision radial velocity instruments coming online
that can detect these compact multi-planet systems can target lower metallicity
stars to find them.
