Large Thermopower of $\delta $-doped LaTiO$_{3}$/SrTiO$_{3}$ Interfaces and it's Field Dependence*

We will present the magneto-thermopower (S(T, H)) of interfacial delta doped LaTiO$_{3}$/SrTiO$_{3}$ heterostructure by an iso-structural antiferromagnetic perovskite LaCrO$_{3}$. The thermoelectric power of 2-dimensional electron gas (2DEG) of pure LaTiO$_{3}$/SrTiO$_{3}$ at 300 K is $\approx $ 118 $\mu $V/K, but increases dramatically to 337 $\mu $V/K on inserting 5 uc LaCrO$_{3}$ at the interface. The negative sign of the thermoelectric power confirms the electron as major carriers in these interfaces. A linear temperature dependence of S(T) has been observed in the temperature range 100 K to 300 K which is in agreement with the theory of diffusion thermopower of 2DEG. The S(T) shows a distinct enhancement at temperature \textless 100 K, where a Kondo-type minimum has been observed in sheet resistance. We attribute this maximum in S(T) to Kondo scattering of conduction electron by localized impurity spin at the interface. The S in this temperature range is suppressed significantly ($\le $ 20{\%}) by moderate magnetic field ($\le $ 13 T) applied either perpendicular or parallel to the film surface. The isotropic nature of the suppression of S by magnetic field further strengthen the Kondo based interpretation of S(T, H).