Nuclear spin clocks are the most accurate clocks (absolute scale) today and therefore very useful for probing physics beyond the Standard Model. Typically two spin species arrangements are used in a comagnetometer setup, in order to get ridge of magnetic field changes caused by the environment. In our experiments we use the two noble gas isotopes 3He and 129Xe. We measure the sinussodial varing (about 10 Hz) magnetization of the free induction decay of our polarized spin species within a very small and a very homogeneous magnetic field (400 nT) with low noise DC-SQUIDS. Depending on the setup, a new hypothetical interaction, sometimes called a fifth force, will cause tiny frequency shift in our setup. After presenting the principles and features of our comagnetometer, I will report on two searches where we are able to set new limits on hypothetical interactions. First we performed a direct search for axion like interactions. Axions are strong candidates for dark matter and therefore in the focus of interest. With a second setup we search for a Lorentz invariance violating preferred frame interactions in a Huges-Drever like experiment.
