Combining unit recording and fMRI is a powerful method that allows for interrogation of the brain at the cellular and network level. However, implanted metal recording electrodes produce susceptibility artifacts that distort MR images. Here, we fabricate single carbon-fiber electrodes and implant them into rat hippocampus and use an agarose phantom to quantify its MR distortion. These carbon-fiber electrodes record from a single unit in CA1 and distort a significantly lower volume of voxels compared to metal electrodes. These results lay the groundwork for an electrode design that can be used for single-unit recording and fMRI in same subjects.