  Within the Coulomb blockade regime, our study delves into the charge, spin,
and thermoelectric transport characteristics in a benzene-based molecular
nano-junction using the Pauli master equation and linear response theory. The
charge- and spin-transport studies show strong negative differential
conductance features in the current-voltage ($I-V$) characteristics for the
ortho and meta connections of electrodes on either side. Contrarily, the
para-connection displays Coulomb staircase behavior. Exploring spin current
behavior in the presence of spin-polarized electrodes or external Zeeman field,
we establish a methodology that facilitates precise control over the specific
spin flow. Various charge and spin thermoelectric transport coefficients have
been studied with varying chemical potentials. We focus on
spin-polarized-conductance, the Seebeck coefficient, and the figure of merit.
By adjusting electrode polarization or employing an external magnetic field, we
achieve an impressive peak value for the spin thermoelectric figure of merit,
approximately 4.10. This outcome underscores the strategic value of harnessing
both spin-polarized electrodes and external magnetic fields within the domain
of spin caloritronics.
