  ZrSiS has recently gained attention due to its unusual electronic properties:
nearly perfect electron-hole compensation, large, anisotropic
magneto-resistance, multiple Dirac nodes near the Fermi level, and an extremely
large range of linear dispersion of up to 2 eV. We have carried out a series of
high pressure electrical resistivity measurements on single crystals of ZrSiS.
Shubnikov-de Haas measurements show two distinct oscillation frequencies. For
the smaller orbit, we observe a change in the phase of 0.5, which occurs
between 0.16 - 0.5 GPa. This change in phase is accompanied by an abrupt
decrease of the cross-sectional area of this Fermi surface. We attribute this
change in phase to a possible topological quantum phase transition. The phase
of the larger orbit exhibits a Berry phase of pi and remains roughly constant
up to 2.3 GPa. Resistivity measurements to higher pressures show no evidence
for pressure-induced superconductivity to at least 20 GPa.
