  We present a detailed investigation of the physical properties of Ce$_2 $Sb
and Ce$_2 $Bi single crystals, which undergo antiferromagnetic transitions at
around 8.2 and 10 K respectively. When magnetic fields are applied parallel to
the $c$ axis, metamagnetic transitions are observed at low temperatures,
corresponding to a magnetic field-induced phase transition. It is found that
the field-induced transition changes from second-order at higher temperatures,
to first-order at low temperatures, suggesting the existence of tricritical
points (TCPs) in both compounds. Since replacing Bi with Sb suppresses the TCP
to lower temperatures and corresponds to a positive chemical pressure, these
results suggest that applying pressure to Ce$_2$Sb may suppress the TCP to
lower temperatures, potentially to zero temperature at a quantum tricritical
point.
