  The Parkes Pulsar Timing Array (PPTA) project monitors two dozen millisecond
pulsars (MSPs) in order to undertake a variety of fundamental physics
experiments using the Parkes 64m radio telescope. Since June 2017 we have been
undertaking commensal searches for fast radio bursts (FRBs) during the MSP
observations. Here, we report the discovery of four FRBs (171209, 180309,
180311 and 180714). The detected events include an FRB with the highest
signal-to-noise ratio ever detected at the Parkes observatory, which exhibits
unusual spectral properties. All four FRBs are highly polarized. We discuss the
future of commensal searches for FRBs at Parkes.
