  Electronic topology in metallic kagome compounds is under intense scrutiny.
We present transport experiments in Na2/3CoO2 in which the Na order
differentiates a Co kagome sub-lattice in the triangular CoO2 layers. Hall and
magnetoresistance (MR) data under high fields give evidence for the coexistence
of light and heavy carriers. At low Ts, the dominant light carrier conductivity
at zero field is suppressed by a B-linear MR suggesting Dirac like
quasiparticles. Lifshitz transitions induced at large B and T unveil the lower
mobility carriers. They display a negative B^2 MR due to scattering from
magnetic moments likely pertaining to a flat band. We underline an analogy with
heavy Fermion physics.
