  We report the hard X-ray properties of the young Crab-like LMC pulsar PSR
B0540-69, using archival RXTE PCA (2 - 60 keV) and RXTE HEXTE (15 - 250 keV)
data. Making use of the very long effective exposure of 684 ks, we derived a
very detailed master pulse profile for energies 2 - 20 keV. We confirm the
broad single-pulse shape with a dip in the middle and with a significant fine
structure to the left of the dip. For the first time pulse profiles in the 10 -
50 keV energy interval are shown. Remarkably, the coarse pulse shape is stable
from the optical up to X-ray energies analogous to the case of the Crab pulsar
(PSR B0531+21). The profiles can be described with two Gaussians with a phase
separation of ~0.2; the distribution of the ratios between the two components
from the optical to the X-ray range is consistent with being flat. Therefore we
cannot conclude that the profile consists of two distinct components. We also
derived a new total pulsed spectrum in the ~0.01 - 50 keV range in a consistent
analysis including also archival ROSAT PSPC (0.01 - 2.5 keV) data. This
spectrum cannot be described by a single power-law, but requires an additional
energy dependent term. The bending of the spectrum around 10 keV resembles that
of the Crab pulsar spectrum. Although model calculations using Outer Gap
scenarios could probably explain the high-energy characteristics of PSR
B0540-69 as they successfully do for the Crab, our measurements do not entirely
agree with the latest calculations by Zhang & Cheng (2000). The small
discrepancies are likely to be caused by uncertainties in the pulsar's
geometry.
