if Xc = Xl then Xc-Xl is zero, so Z series is zero so in the ohms law equation...
Vt = I*Z
Vt = I*(zero)
... or realistically, Z series "approaches" zero (as related to limits in calculus)
... thus I must "approach" infinity as Z approaches zero to maintain any sort of voltage
series LC resonance will yield maximum current and low voltage
what we really want is parallel LC (or RLC) resonance...
in parallel LC resonance you get maximum current impedance, and infinite voltage.
Look at the VIC matrix circuit, you will see the self capacitance of the resonance charging chokes are in parallel with the inductance giving you a parallel RLC circuit
Note that the capacitance of the resonant cavity has to be small otherwise it would get in the way of the parallel resonance because the resonant cavity is in series!