THE MAGNETIC PHASE-DIAGRAM AND TRANSPORT-PROPERTIES OF FEGE2

We have used resistivity measurements to study the magnetic phase diag ram of the itinerant antiferromagnet FeGe2 in the temperature range fr om 0.3-300 K in magnetic fields up to 16 T. In contrast to theoretical predictions, the incommensurate spin-density-wave phase is found to b e stable at least up to 16 T, with an estimated critical field mu(o)H( c) of similar to 30 T. We have also studied the low-temperature magnet oresistance in the [100], [110], and [001] directions. The transverse magnetoresistance is well described by a power law for magnetic fields above 1 T with no saturation observed at high fields. We discuss our results in terms of the magnetic structure and the calculated electron ic band-structure of FeGe2. We have also observed, for the first time in this compound, Shubnikov-de Haas oscillations in the transverse mag netoresistance with a frequency of 190 +/- 10 T for a magnetic field a long [001].