Metallization and magnetic order in EuB6

We present the results of field- and temperature-dependent resistivity rho and magnetization M measurements which show that colossal magnetoresistance in semimetallic EuB6 is not associated with its bulk Curie temperature T-C =12.6 K, determined by a scaling analysis of M(H,T), but with a second phas e transition at T-M=15.5 K. We propose that metallization occurs at T-M via the overlap of magnetic polarons. The separation of the charge delocalizat ion and bulk magnetic ordering transitions implies electronic and magnetic phase separation.