Depolarization of muonium due to superhyperfine interaction, which until now has severely impeded the study of muonium in solids, can be quenched in a high transverse magnetic field (1.2 T). We report the observation of muonium precession in single crystals of KCl, CaF2, GaP, and Al2O3. The high-field frequencies are of order 2 GHz and provide a direct and accurate (60 ppm) measure of the hyperfine interval. Several novel features of the muonium centers are observed. © 1984 The American Physical Society.