MAGNETORESISTANCE OF THE KONDO INSULATOR CE3BI4PT3

The magnetoresistance (MR) of the narrow-gap Kondo insulator Ce3Bi4Pt3 and its non-magnetic analog La3Bi4Pt3 have been measured in magnetic fields to 10T and in the temperature range 2-300 K. Ce3Bi4Pt3 exhibits a large negative MR component below 7 K. At higher temperatures this negative component progressively decreases and a positive contribution becomes evident. Above 75 K the MR is positive at all fields and saturates to a value of a few percent. The non-magnetic analog La3Bi4Pt3 exhibits the same positive magnetoresistance present in Ce3Bi4Pt3 as well as a conventional positive H-2 term at low temperatures. We discuss potential mechanisms for both the common positive effect and the large negative MR present in Ce3Bi4Pt3.