  The shape of the Fermi surface, and the cyclotron effective mass of the
kagome magnet GdV6Sn6 charge carriers are investigated using de Haas van Alphen
(dHvA) oscillations measurements and electronic band structure calculations.
The temperature and angle-dependent torque magnetometry measurements revealed
at least nine different frequencies ranging from ~10 T up to ~9000 T. These
frequencies correspond to extremal areas of the Fermi surface ranging from ~0.2
% up to 50% of the first Brillouin zone, qualitatively consistent with the
electronic band structure calculations. The angle dependent dHvA oscillation
frequencies indicate that the smaller pockets of the Fermi surface have almost
3D character whereas the bigger pockets of the Fermi surface are mostly
two-dimensional. We also find evidence of the presence of light (0.28(1) m0) as
well as heavy (2.37(18) m0) charge carriers through the analysis of the
temperature dependence of dominant frequencies. The comparison of the observed
frequencies with the electronic band structure calculations indicates that the
heavy masses correspond to saddle-point-like features of electronic band
structure at the M point. The observation of the multiple low frequencies and
the calculated contributions from various bands to such low frequencies prevent
the estimation of topological nature of bands containing lighter fermions. In
conclusion, our work reveals the features of a Fermi surface containing
enhanced mass fermions originated from saddle points in the electronic band
structure at the M point, which is inherent to kagome lattices.
