  The study of kagome materials has attracted much attention in the past few
years due to the presence of many electron-electron interaction-driven phases
in a single material.In this work, we report the discovery of intrinsic
spin-polarized p-wave superconductivity in the thin-flake kagome material
RbV$_3$Sb$_5$. Firstly, when an in-plane magnetic field is swept in opposite
directions, we observe a unique form of hysteresis in magnetoresistance which
is different from the hysteresis induced by extrinsic mechanisms such as
flux-trapping or superheating and supercooling effects. The unconventional
hysteresis indicates the emergence of an intrinsic time-reversal
symmetry-breaking superconducting phase. Strikingly, at a fixed magnetic field,
the finite-resistance state can be quenched to the zero-resistance state by
applying a large current. Secondly, at temperatures around 400 mK, the
re-entrance of superconductivity occurs during an in-plane field-sweeping
process with a fixed sweeping direction. This kind of re-entrance is asymmetric
about the zero field axis and observed in all field directions for a fixed
current direction, which is different from the re-entrance observed in
conventional superconductors. Moreover, the angle-dependent in-plane critical
field measurements reveal a two-fold symmetry that deviates from the original,
centrosymmetric D$_{6h}$ point group symmetry of the crystal. These findings
put very strong constraints on the possible superconducting pairing symmetry of
RbV$_3$Sb$_5$. We point out that the pairing symmetry, which is consistent with
the crystal symmetry and all the observed novel properties, is a time-reversal
symmetry-breaking, p-wave pairing with net spin polarization. Importantly, this
p-wave pairing gives rise to a nodal topological superconducting state with
Majorana flat bands on the sample edges.
