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An equality of particle and antiparticle gravitational interactions holds in general relativity and is supported by indirect observations. Gravity dependence on rotation or spin direction is experimentally constrained for non-relativistic matter. Here, a method based on high-energy Compton scattering is developed to measure the gravitational interaction of accelerated charged particles. Within that formalism, the Compton spectra measured at HERA rule out the speculated anti-gravity possibility for antimatter at a confidence level close to 100%. The same data, however, imply a gravitational CP violation around 13 GeV energies, by a maximal amount of (9 ± 2) ⋅ 1 0 − 1 2 for the charge and (1 3 ± 3) ⋅ 1 0 − 1 2 for the space parity. The detected asymmetry hints for a stronger gravitational coupling to left helicity electrons relative to right helicity positrons. [ABSTRACT FROM AUTHOR]