Giant galvanomagnetic effects in intermediate valence systems with magnetic order

It was found that in some samples of CeMn2-xSi2+x composition giant galvanomagnetic effects may be observed. The magnetoresistance [R(H,T) -R(0,T)]/R(0,T) at a temperature of 4.2 K can change from 70% for CeMn2.00Si2.00 up to 230% for CeMn2.10Si1.90 composition in a magnetic field of 13 T. In CeMn1.95-1.80Si2.05-2.20 samples the magnetoresistance is negative and small (-5%); thus the substitution Mn --> Si suppresses the giant magnetoresistance. The reason of the giant galvanomagnetic effects may be the appearance of a narrow gap in a magnetic field due to the presence of intermediate valence states of Ce and antiferromagnetic order of the Mn sublattice.