Periodic orbit resonances in kappa-(ET)(2)I-3

We have observed periodic orbit resonances in the normal state of the organ ic superconductor kappa-(ET)(2)I-3 Frequency dependent studies allow for a determination of the cyclotron mass, which can then be compared with the ef fective mass obtained by other techniques. Tilting the sample in the applie d magnetic field enhances the resonance harmonics and enables investigation of the warping of the nearly cylindrical Fermi surface; our findings confi rm recent theoretical predictions for quasi-two-dimensional conductors.