  We present a de Haas-van Alphen study of the Fermi surface of the low
temperature antiferromagnet CeZn11 and its non-magnetic analogue LaZn11,
measured by torque magnetometry up to fields of 33T and at temperatures down to
320 mK. Both systems possess similar de Haas-van Alphen frequencies, with three
clear sets of features - ranging from 50T to 4kT - corresponding to three bands
of a complex Fermi surface, with an expected fourth band also seen weakly in
CeZn11. The effective masses of the charge carriers are very light (<1 me) in
LaZn11 but a factor of 2 - 4 larger in CeZn11, indicative of stronger
electronic correlations. We perform detailed density functional theory (DFT)
calculations for CeZn11 and find that only DFT+U calculations with U=1.5 eV,
which localize the 4f states, provide a good match to the measured de Haas-van
Alphen frequencies, once the presence of magnetic breakdown orbits is also
considered. Our study suggests that the Fermi surface of CeZn11 is very close
to that of LaZn11 being dominated by Zn 3d, as the Ce 4f states are localised
and have little influence on its electronic structure, however, they are
responsible for its magnetic order and contribute to enhance electronic
correlations.
