FIG. 5: Resistive measurements of a sample prepared at 5 Hz under optimized conditions. The data were achieved using a four-point probe at T / t = 1 K/min (R( T ) from 2 to 300 K: 5 K/min) and at a measurement current I = 1 mA. (a) R( T ) measurement in the absence of an external magnetic field exhibiting a residual resistivity ratio of about 15. The superconducting transition with a ΔT$_{c}$ ≈ 0.3 K is shown in the inset. (b) R(T) at different external magnetic fields aligned parallel to the [001] borocarbide crystallographic axis. this temperature. Thus, deposition temperatures around 840 ℃ are kept during further op- timization of the deposition conditions. Consequently, the T$_{c}$ values resistively determined from samples fabricated under optimized deposition conditions ( T = 830 ℃ , f = 5 Hz) of up to 15.8 K are considerably closer to the optimum and typically sharp ΔT$_{c}$ < 0.3 K are 9