  In the context of the LENS R&D solar neutrino project, the gamma spectrum of
a sample of metallic indium was measured using a single experimental setup of 4
HP-Ge detectors located underground at the Gran Sasso National Laboratories
(LNGS), Italy. A gamma line at the energy (497.48 +/- 0.21) keV was found that
is not present in the background spectrum and that can be identified as a gamma
quantum following the beta decay of In-115 to the first excited state of Sn-115
(9/2+ --> 3/2+). This decay channel of In-115, which is reported here for the
first time, has an extremely low Q-value, Q = (2 +/- 4) keV, and has a much
lower probability than the well-known ground state-ground state transition,
being the branching ratio b = (1.18 +/- 0.31) 10^-6. This could be the beta
decay with the lowest known Q-value. The limit on charge non-conserving beta
decay of In-115 is set at 90% C.L. as tau > 4.1 10^20 y.
