  In this paper we present a consolidated equation for all low-field transport
coefficients, based on a reservoir approach developed for non-interacting
quasiparticles. This formalism allows us to treat the two distinct types of
charged (fermionic and bosonic) quasiparticles that can be simultaneously
present, as for example in superconductors. Indeed, in the underdoped cuprate
superconductors these two types of carriers result in two onset temperatures
with distinct features in transport: $T^*$, where the fermions first experience
an excitation (pseudo)gap, and $T_c$, where bosonic conduction processes are
dominant and often divergent. This provides the central goal of this paper,
which is to address the challenges in thermoelectric transport that stem from
having two characteristic temperatures as well as two types of charge carriers
whose contributions can in some instances enhance each other and in others
compete. We show how essential features of the cuprates (their "bad-metal"
character and the presence of Fermi arcs) provide an explanation for the
classic pseudogap onset signatures at $T^*$ in the longitudinal resistivity,
$\rho_{xx}$. Based on the fits to the temperature-dependent $\rho_{xx}$, we
present the implications for all of the other thermoelectric transport
properties.
