Magnetism and heavy fermions in YbRhSn and YbPtSn

Isostructural YbRhSn and YbPtSn were studied by specific heat, electrical r esistivity, and magnetoresistance. Both compounds order antiferromagnetical ly below 2 and 3.5 K, respectively. Above 4 K, they display a number of rem arkable similarities including Kondo-like resistivity and large negative ma gnetoresistance. Scaling analysis of this magnetoresistance shows that it i s due to the suppression of Kondo scattering in YbRhSn but has a ferromagne tic spin fluctuation character in YbPtSn. The heavy fermion state was confi rmed in YbRhSn by low temperature specific heat measurements yielding gamma of about 1200 mJ/K-2 mol. gamma for YbPtSn is of order 100 mJ/K-2 mol only . (C) 2000 American Institute of Physics. [S0021-8979(00)90108-7].