First off, I'm pretty sure I won't be able to get a definite answer here, just looking for some suggestions. In a physics lab last week, we observed some anomalous effects. First off, let me describe what we did. We were looking at the Hall effect using SiAs with an As concentration approx. 4*10^18/m^3. Applied a potential difference (6V) across the specimen (4.0mm, 16.0mm, 0.47mm) with an orthoganal magnetic field (0.97 T). The interesting thing occured as we increased the magnetic field from zero. The current through our circuit decreased by about 7% as we increased the magnetic field from 0 to 0.97 T. At all magnetic field strengths V=IR still held (R^2 > 0.9999). Since it was not the aim of the prac to investigate this, and we get marked on it, we couldn't spend too much time experimenting. Our demonstrators weren't able to explain it. I'm wondering if this could be due to magnetoresistance or if something else could explain it?