  Kondo-based semimetals and semiconductors are of extensive current interest
as a viable platform for strongly correlated states. It is thus important to
understand the routes towards such dilute-carrier correlated states. One
established pathway is through Kondo effect in metallic non-magnetic analogues.
Here we advance a new mechanism, through which Kondo-based semimetals develop
out of conduction electrons with a low carrier-density in the presence of an
even number of rare-earth sites. We demonstrate this effect by studying the
Kondo material Yb3Ir4Ge13 along with its closed-f-shell counterpart,
Lu3Ir4Ge13. Through magnetotransport, optical conductivity and thermodynamic
measurements, we establish that the correlated semimetallic state of Yb3Ir4Ge13
below its Kondo temperature originates from the Kondo effect of a low carrier
conduction-electron background. In addition, it displays fragile magnetism at
very low temperatures, which, in turn, can be tuned to a non Fermi liquid
regime through Lu-for-Yb substitution. These findings are connected with recent
theoretical studies in simplified models. Our results open an entirely new
venue to explore the strong correlation physics in a semimetallic environment.
