Asymptotic power-law tails of massive scalar fields in a Reissner-Nordström background

We investigate the dominant late-time tail behavior of massive scalar fields in a nearly extreme Reissner-Nordstr\"om background. It is shown that the oscillatory tail of the scalar fields has the decay rate of t^-5/6 at asymptotically late times. The physical mechanism by which the asymptotic t^-5/6 tail is generated and the relation between the field mass and the time scale when the tail begins to dominate are discussed in terms of resonance backscattering due to space-time curvature.