  We report high field (up to 13 Tesla) magneto transport R(T)H] of YBa2Cu3O7
(YBCO):Agx (x= 0.0, 0.1 and 0.2) composites. The transport properties are
significantly improved by Ag doping on the insulating grain boundaries of YBCO.
Pure and Ag diffused YBCO superconducting samples are synthesized through solid
state reaction route. Both pure and Ag doped YBCO are superconducting at below
90K. Though, the Tc (R=0) of YBCO:Ag samples under applied field of 13 Tesla is
around 65K, the same is 45K for pure YBCO under same applied field. The upper
critical field [Hc2(0)], being estimated from R(T)H is around 70Tesla for
pristine sample, and is above 190Tesla for Ag doped samples. The boarding of
the resistive transition under applied magnetic field is comparatively less and
nearly single step for Ag doped samples, while the same is clearly two step and
relatively much larger for the pristine YBCO. The resistive broadening is
explained on the basis of changed inter-granular coupling and thermally
activated flux flow (TAFF). The TAFF activation energy (U0) is found to be
linear with applied magnetic field for all the samples, but with nearly an
order of magnitude less value for the Ag doped samples. Summarily, it is shown
that inclusion of Ag significantly improves the superconducting performance of
YBCO:Ag composites, in particular under applied field.
