The valence-skipped superconductors are natural candidates for unconventional
superconductivity, as they can exhibit a negative effective, attractive
interaction for electron-pairing. This work reports comprehensive XRD,
magnetization, specific heat and muon spin rotation and relaxation measurements
(μSR) on a valence-skipped compound: AgSnSe2​. The temperature dependence
of the electronic specific heat (Cel​(T)) and of the upper critical field
(Hc2​(T)) provide evidence of two-gap superconductivity, which is also
confirmed by our transverse-field μSR measurements. Our zero-field μSR
measurements suggest preserved time-reversal symmetry in the superconducting
ground state of AgSnSe2​.Comment: 8 pages, 6 figure