The understanding of the pairing mechanism in unconventional superconductors is a major theoretical challenge. Recent muon-spin relaxation measurements of the heavy-fermion superconductor filled-skutterudite PrOs4Sb12 reveal the spontaneous appearance of static internal magnetic fields below the Tc, providing unambiguous evidence for the breaking of time-reversal symmetry in the superconducting state. LaRu4As12 and LaOs4As12 is also a filled-skutterudite compound, with Tc = 10.3 K and 3.2 K respectively. The Tc of LaRu4As12 (multiple superconducting gaps) is the highest in these compounds. For LaOs4As12 the temperature dependences of the nuclear spin?lattice relaxation rates of 75As nuclei can be understood in terms of antiferromagnetic spin fluctuations (ASF). We want to study these compounds by zero-field and transverse field µSR technique using MUSR spectrometer.