  According to the Bardeen-Cooper-Schrieffer (BCS) theory, superconductivity
usually needs well defined Fermi surface(s) with strong electron-phonon
coupling and moderate quasiparticle density of states (DOS). A kagome lattice
can host flat bands and topological Dirac bands; meanwhile, due to the parallel
Fermi surfaces and the saddle points, many interesting orders are expected.
Here, we report the observation of superconductivity by pressurizing a kagome
compound Rb$_2$Pd$_3$Se$_4$ using a DAC anvil. The parent compound shows an
insulating behavior; however, it gradually becomes metallic and turns to a
superconducting state when a high pressure is applied. High pressure
synchrotron measurements show that there is no structural transition occurring
during this transition. The density-functional-theory (DFT) calculations
illustrate that the insulating behavior of the parent phase is due to the
crystalline field splitting of the partial Pd-4d $t_{2g}$ bands and the
Se-derivative 4$p$-band. However, the threshold of metallicity and
superconductivity are reached when the Lifshitz transition occurs, leading to
the emergence of tiny Fermi surface at $\Gamma$ point. Our results point to an
unconventional superconductivity and shed new light on understanding the
electronic evolution of a kagome material.
