Thin ribbons of stable icosahedral quasicrystal Al65Cu20Fe15 were irradiated with swift heavy ion (SHI) beam of 170 million electron volt (MeV) 58Ni+12 in high and clean vacuum environment at a temperature of 80 K to study the modification of its properties. Dynamic variation of resistance was studied on-line during and after irradiation for the first time, to understand the effect of SHI. The resistance decreased sharply at the time of incidence of ion beam due to creation of a large number of charge carriers by intense ionization by SHI and did oscillate around a mean value during irradiation due to defect creation and annihilation. The resistance increased rapidly just after the beam was stopped from its mean value during irradiation. The quasicrystalline peaks of the XRD data on these samples irradiated by SHI, were prominent till the ion beam fluence of 5 × 1012 particles/cm2, but the peak height consistently decreased with increasing fluence after a fluence of 1012 particles/cm2. © 2001 Elsevier Science Ltd. All rights reserved.