The angular dependence of the upper critical field H c2(θ, Φ, T) of UPt 3 in magnetic fields up to 3T has been measured. We performed angular resolved magnetoresistance measurements to determine the change in anisotrophy of H c2(Θ) between the hexagonal plane and the c-axis throughout the phase diagram. Furthermore, in single crystals with a rectangular cross-section, a sixfold modulation of the N c2(Θ) is observed at the superconducting transition in the basal plane, which cannot be related to geometry dependent surface superconductivity effects. This modulation vanishes as the temperature approaches T ∗ (the temperature of the discontinuity in slope of H c2(T)) and reappears for T< T ∗ but with opposite sign. The results provide new evidence on the unconventional nature of the superconducting order parameter and its coupling with antiferromagnetism.