A few years ago we observed anomalous electron-positron angular correlations for the 18.15 MeV M1 transition of ⁸Be. This was interpreted as the creation and decay of an intermediate bosonic particle with a mass of m₀c²=16.70±0.35(stat )±0.5(sys) MeV, which is now called X17. The possible relation of the X17 boson to the dark matter problem triggered an enormous interest in the wider physics community. We also observed a similar anomaly in ⁴He, which could be described also by the creation and subsequent decay of the same X17 particle. Very recently, the ¹¹B proton capture reaction was used for exciting the 17.2 MeV broad (Γ=1.15 MeV) resonance in ¹²C and studying their internal pair creation decay. Anomalies were observed in the angular correlation of the electron-positron pairs, which together with the ⁸Be and ⁴He data provides kinematic evidence for the X17 particle and supports their vector boson and fifth force explanation.