A search is performed for the as yet unobserved baryonic b0 and b0 decays with 3 fb1 of proton-proton collision data recorded by the LHCb experiment. The B0Ks0 decay is used as a normalisation channel. No significant signal is observed for the b0 decay. An upper limit is found on the branching fraction of $$ \mathrm{\mathcal{B}}\left({\Lambda}_{\mathrm{b}}^0\to \Lambda \upeta^{\prime}\right) $$< 3.1 × 106 at 90% confidence level. Evidence is seen for the presence of the b0 decay at the level of 3 significance, with a branching fraction $$ \mathrm{\mathcal{B}}\left({\Lambda}_{\mathrm{b}}^0\to \Lambda \upeta \right) = \left(9.{3}_{-5.3}^{+7.3}\right)\times 1{0}^{-6} $$.
