Observations of acoustic de Haas-van Alphen effect in alpha-(ET)(2)NH4Hg(SCN)(4)

The acoustic de Haas-van Alphen (dHvA) effect is observed as a function of magnetic field for the longitudinal ultrasound frequency 53.4 MHz traveling along the b' direction in the quasi-two-dimensional superconductor alpha-( ET)(2)NH4Hg(SCN)(4) with T-c similar to 1 K. From calculating the oscillato ry amplitude with the use of the Kataoka and Goto formulations, the area co efficient relating to the electron-lattice coupling is estimated to be abou t 3.5. The dominant contribution comes from the multiband term correspondin g to the inter-band charge transfer. The anomaly in the longitudinal veloci ty around 20 and 60 K is also described.