Emergent spin-singlet pairing in the frustrated kagome metal Sc 3 Mn 3 Al 7 Si 5

The metallic kagome compound Sc 3 Mn 3 Al 7 Si 5 has attracted attention as a candidate platform where geometric frustration and itinerant electrons may cooperate to stabilize a quantum-disordered magnetic ground state. Here, we combine bulk thermodynamic probes, low-noise focused-ion-beam-device transport, and comprehensive Mn 55 nuclear magnetic resonance (NMR) measurements to elucidate the low-temperature spin dynamics of this system. The bulk data reveal strongly reduced magnetic entropy, a negative magnetoresistance arising from spin scattering, and field-dependent transport indicates the spin fluctuations, while showing no signatures of long-range magnetic order. NMR provides a direct local view of the correlated Mn moments: the nuclear spin-spin relaxation time T 2 exhibits a pronounced low-temperature enhancement driven by an indirect internuclear coupling through electronic spin fluctuations, whose temperature and distance dependencies point to partially gapped low-energy spin excitations. The spin-lattice relaxation rate T 1 − 1 displays a broad peak near 10 K that may originate from spin-singlet pairing and coincides with the resistivity crossover and a subtle heat-capacity anomaly. Together, our results suggest that Sc 3 Mn 3 Al 7 Si 5 hosts an unconventional correlated state dominated by frustrated, gapped spin dynamics, placing it among the rare metallic kagome systems proximate to a quantum spin liquid.