We report the results of a first experimental search for lepton number violation by four units
in the neutrinoless quadruple-β decay of 150Nd using a total exposure of 0.19 kg·y recorded with
the NEMO-3 detector at the Modane Underground Laboratory (LSM). We find no evidence of this
decay and set lower limits on the half-life in the range T1/2 > (1.1–3.2) × 1021 y at the 90% CL,
depending on the model used for the kinematic distributions of the emitted electrons
