By analyzing e^+e^- annihilation data corresponding to an integrated luminosity of 7.93 fb^{-1}, collected at the center-of-mass energy of 3.773 GeV with the BESIII detector, we search for the semileptonic decays D^0\to K^-\eta e^+\nu_e, D^+\to K_S^0 \eta e^+\nu_e and D^+\to \eta\eta e^+\nu_e for the first time. We present evidence for... Show more