We select models out of each cost group that are close to the Pareto front for both the train and test RMSE. In the lower-cost group M 4,1 and M 3,1 yield the lowest RMSE of 0.15 eV and 0.16 eV, respectively, for the training set. However, their performance for the test set is significantly worse with RMSEs of 0.27 eV and 0.28 eV, respectively. In comparison, M 1,3 yields a similar train RMSE of 0.16 eV and a lower test RMSE of 0.24 eV. For this reason, we select M 1,3 out of the lower-cost group: