Abstract
For pt.I see ibid., vol.5, p.935 (1993). Studies of the Faraday rotation in TbPO4 confirmed the known properties of the different low-temperature phases. Unexpected oscillations, however, were observed in the temperature dependence of the measured rotation in one of the low-symmetry phases. Model calculations of the rotation for a material possessing both Faraday rotation and birefringence did allow an interpretation of the findings, but rather unusual properties of the substance have to be assumed. These calculations additionally showed that the method of measurement influences the results in a typical way so that the optical properties of the substance cannot always be derived directly from the experimental curves.