An anisotropic electron mobility has recently been reported in 4H-SiC MOS devices with improved inversion layer mobility [1]. This anisotropy arises from scattering by oriented steps on the 8degrees off-axis 4H-SiC surface. The mobility is higher in the direction parallel to the steps, and lower perpendicular to the steps. In this paper, we describe anomalous behavior observed in the sheet resistance measurement in a van der Pauw (VDP) device which is caused by the anisotropy. Experimentally, a similar to15% mobility anisotropy results in a 1.8x anisotropy in the VDP sheet resistance. This surprising experimental result is confirmed by numerical simulations.