Very recently Sato et al., JPSJ 2018 have investigated superconductivity in the single crystals of CeIr3 (Tc = 3.4 K, which is highest among Ce compounds), which shows a weak coupling BCS regime. Further LaIr3 having no 4f-electron also exhibits superconductivity with Tc = 3.3 K, so it is an open question what is the role of 4f-electron in CeIr3? Electronic band structure calculations of LaIr3 show that Ir d-states dominate the Fermi level indicating presence of strong spin–orbit-coupling with a complex Fermi surface. In this proposal, we want to perform the muon spin rotation study to investigate the pairing mechanism, time reversal symmetry and spin-fluctuations in CeIr3 and LaIr3. As other groups will also measure these interesting materials using their muon facilities, we would like to submit this proposal as a Rapid Access to get a fast publication in the high impact journal.