  The connection between unconventional superconductivity and charge density
waves (CDW) has intrigued the condensed matter community and found much
interest in the recently discovered superconducting Kagome family of
AV$_3$Sb$_5$ (A = K, Cs, Rb). Xray diffraction and Raman spectroscopy
measurements established that the CDW order in CsV$_3$Sb$_5$ comprises of a
2x2x4 structure with stacking of layers of star-of-David (SD) and
inverse-star-of-David (ISD) pattern along the $c$-axis direction. Such
interlayer ordering will induce a vast normalization of the electronic ground
state; however, it has not been observed in Fermi surface measurements. Here we
report quantum oscillations of CsV$_3$Sb$_5$ using tunnel diode oscillator
frequency measurements. We observed a large number of frequencies, many of
which were not reported. The number of frequencies can not be explained by DFT
calculations when only SD or ISD distortion is considered. Instead, our results
are consistent with calculations when interlayer ordering is taken into
account, providing strong evidence that CDW phase of CsV$_3$Sb$_5$ has
complicated structure distortion which in turn has dramatic effects on the
Fermi surface properties.
