  We report superconducting properties of AgSnSe2 which is a conventional
type-II superconductor in the very dirty limit due to intrinsically strong
electron scatterings. While this material is an isotropic three-dimensional
(3D) superconductor with a not-so-short coherence length where strong vortex
fluctuations are NOT expected, we found that the magnetic-field-induced
resistive transition at fixed temperatures becomes increasingly broader toward
zero temperature and, surprisingly, that this broadened transition is taking
place largely ABOVE the upper critical field determined thermodynamically from
the specific heat. This result points to the existence of an anomalous metallic
state possibly caused by quantum phase fluctuations in a strongly-disordered 3D
superconductor.
