Electromagnetic transition rates provide an important test for nuclear structure models. The nucleus ⁸Be exhibits a pronounced alpha-cluster structure and is a building block for more complex cluster nuclei. Here we report on the first observation of the gamma transition between the 4⁺and 2⁺ states of  ⁸Be in the ⁴He+⁴He reaction. The measured on-resonance cross section of 165 ±54 nb leads to a B(E2) of 25±8 e²fm⁴, in good agreement with alpha-cluster models and sophisticated ab initio structure calculations