  We report quantum oscillation measurements on the kagome compounds
ATi$_3$Bi$_5$ (A=Rb, Cs) in magnetic fields up to 41.5 T and temperatures down
to 350 mK. In addition to the frequencies observed in previous studies, we have
observed multiple unreported frequencies above 2000 T in CsTi$_3$Bi$_5$ using a
tunnel diode oscillator technique. We compare these results against density
functional theory calculations and find good agreement with the calculations in
the number of peaks observed, frequency, and the dimensionality of the Fermi
surface. For RbTi$_3$Bi$_5$ we have obtained a different quantum oscillation
spectrum, although calculated quantum oscillation frequencies for the Rb
compound are remarkably similar to the Cs compound, calling for further
studies.
