Enhancement of charge-neutral fermionic excitations near the spin-flop transition in the magnetic Kondo material <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>YbIr</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi>Si</mml:mi><mml:mn>7</mml:mn></mml:msub></mml:mrow></mml:math>

The new Kondo material YbIr$_3$Si$_7$, similar to other insulators, has been reported exhibit charge-neutral fermionic excitations through measurements of specific heat and thermal conductivity at low temperatures. We performed $^{29}$Si-NMR on YbIr$_3$Si$_7$ investigate the magnetic response fermions from a microscopic perspective. In fields parallel $c$ axis, single NMR peak in paramagnetic state splits into three peaks below $T_{\rm N}$. contrast, only slight shift was observed high fields. This spectral change as function $c$-axis field is interpreted spin-flop transition, which moments oriented along axis (AF-I phase) are rotated $ab$ plane with ferromagnetic component (AF-II phase). vicinity $H_{\rm M}$, nuclear spin-lattice relaxation rate $1/T_1$ found be proportional temperature temperatures, indicating existence fermions. Furthermore, vs. suggests that closely related its properties. Our findings shed light origin insulators.