Effect of Ce impurities on superconductivity and nuclear spin-lattice relaxation in La1−cCecAl2

In the superconducting state of La_1?cCe_cAl₂ alloys ¹³⁹La spin-lattice relaxation times T_1s for relatively high c were found to agree with theory based on weak exchange coupling between conduction electrons and paramagnetic impurities. But for a dilute specimen the measured values of T_1s are significantly longer than expected. These results are tentatively attributed to the existence of a localized impurity band within the superconducting energy gap.