We investigate the microscopic properties of the kagome compound ${\mathrm{Cs}}_2{\mathrm{Cu}}_3{\mathrm{SnF}}_{12}$ using ${}^{63,65}\mathrm{Cu}$ nuclear quadrupolar resonance. Analysis of the local hyperfine fields below the Néel temperature $T_{\mathrm{N}}=20\mathrm{K}$ indicates a spin structure consistent with $P{2}_1/n$ symmetry of negative vector chirality. Measurements of the spin-lattice relaxation rate $T_1^{-1}$ reveal signatures of a gapless ground state and two-dimensional Berezinskii-Kosterlitz-Thouless–type correlations above $T_{\mathrm{N}}$, extending over a broad temperature range of approximately 130 K in zero magnetic field. Within the same temperature range, the observed increase in the nuclear quadrupolar resonance linewidth is consistent with short-range chiral order recently identified by neutron scattering. Our results establish ${\mathrm{Cs}}_2{\mathrm{Cu}}_3{\mathrm{SnF}}_{12}$ as a unique quantum kagome system exhibiting Berezinskii-Kosterlitz-Thouless behavior.

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• Antiferromagnetism
• BKT transition
• Frustrated magnetism
• Magnetic anisotropy
• Magnetic order
• Spin dynamics
• Nuclear magnetic resonance
• Nuclear quadrupole resonance