A series of Te-substituted pyrochlores of stoichiometry ${\mathrm{Tl}}_{2}{\mathrm{Mn}}_{2\ensuremath{-}x}{\mathrm{Te}}_{x}{\mathrm{O}}_{7}$ $(x<~0.2)$ has been prepared under high-pressure conditions, at 20 kbar. A neutron-diffraction study demonstrates that Te atoms partially replace Mn cations, adopting a hexavalent oxidation state. The samples are ferromagnetic (FM), showing a maximum ${T}_{C}$ of 193 K for the $x=0.1$ member, considerably higher that that of undoped compound ${\mathrm{Tl}}_{2}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7},$ with ${T}_{C}=120$ K. This trend implies the reinforcement of an extra FM superexchange interaction mediated by the conduction band. Hall effect shows a dramatic increase in the number of carriers upon Te doping, implying an electronic injection associated with the replacement of ${\mathrm{Mn}}^{4+}$ by the aliovalent ${\mathrm{Te}}^{\mathrm{VI}}.$ The magnetoresistance (MR) is lower than that observed for the undoped pyrochlore, as expected for a higher number of carriers. The high temperature resistivity can be modeled by a thermally activated behavior, via magnetic polaron hopping. The activation energy decreases upon Te doping, which also suggests an overall enhancement of the FM interactions in the conduction matrix.