LOW-TEMPERATURE MAGNETORESISTANCE OF UPD2AL3 THIN-FILMS

The transverse magnetoresistance Delta rho/rho(B,T)=(rho(B,T)-rho(0,T) )/rho(0,T) of epitaxial UPd2Al3 thin films with various defect densiti es has been measured in the temperature range from 2K to 35K and in ma gnetic fields up to 12T. Whereas in films with low defect densities De lta rho/rho for ($) under bar B parallel to ($) under bar c shows a st rong positive magnetoresistance (up to 15% at (12T,2K)) due to the for mation of a coherent band of heavy quasiparticles, we find a negative magnetoresistance in films with high defect concentration which is exp ected for a Kondo system in the incoherent regime. For ($) under bar B perpendicular to ($) under bar c a local maximum in the (B,T)-plane o f Delta rho/rho can be resolved near (4T,6K).