A faint MUV = -14. 5 Lyman-continuum leaker candidate in the epoch of reionization: Unprecedented Lyα properties at z=5. 725

We report the unprecedented Lyα properties of AMORE6, an extremely metal-poor (12+łog (̊m O/H) < 6), low-mass (M_⋆ = 4. 4, M_⊙), and ultracompact (effective radius sim30 pc) dwarf galaxy at z=5. 7253, which is gravitationally lensed by the cluster A2744. A prominent, narrow, and nearly symmetric Lyα emission line is detected at the systemic redshift (the latter traced by Hβ, from 5 slitless spectroscopy), with a rest-frame equivalent width of 150 ± 10 Å, a full width at half maximum of ̊m 58, and a slight asymmetry, resulting in a flux excess of ̊m km s -1 in the red wing of the line. The negligible velocity offset from systemic (dv = 4 km s^-1, 3σ uncertainty), together with the sharpness and symmetry of the profile, indicates minimum radiative transfer effects, which implies a neutral hydrogen column density consistent with an optically thin medium that in turn is compatible with a nonzero ionizing photon escape fraction. If indirect spectral diagnostics calibrated at z<4. 5 remain the only viable tools for identifying LyC leakers during reionization, then based on its strongest indicator (Lyα), AMORE6 stands out as one of the most compelling LyC-leaking candidates yet discovered in the epoch of reionization.