  We present high-field magnetotransport properties of high-quality
single-crystalline thin films of heavily underdoped nonsuperconducting
(La,Ce)2CuO4, (Pr,Ce)2CuO4, and (Nd,Ce)2CuO4. All three materials show
identical behavior. They are metallic at high temperatures and show an
insulating upturn at low temperatures. The insulating upturn has a log T
dependence, but saturates toward the lowest temperatures. Notably, the
insulating upturn tends to be suppressed by applying magnetic fields. This
negative magnetoresistance has a log B dependence, and its anisotropy shows non
simple behavior. We discuss these findings from the viewpoints of Kondo
scattering and also two-dimensional weak localization, and demonstrate Kondo
scattering as a more plausible explanation. The Kondo scatters are identified
as Cu2+ spins in the CuO2 planes.
