  We report a discovery of superconductivity with Tc = 5.5 K in Nb2PdxSe5, in
which one-dimensional (1D) Nb-Se chains existing along the b-direction
hybridize each other to form the conducting b-c* plane. The magnetic
susceptibility and specific heat data in both single- and poly-crystals show
evidence of bulk superconductivity. The resistivity, Hall coefficient, and
magneto-resistance data all indicate the presence of an energy scale T* = ~ 50
K, which becomes systematically lowered under hydrostatic pressure and competes
with the stabilization of superconductivity. Combined with the band calculation
results showing the Fermi surfaces with 1D character, we postulate that the
energy scale T* is related to a formation of a density wave or a stabilization
of low dimensional electronic structure. The zero temperature upper critical
field, Hc2(0), of the single crystal is found to be 10.5, 35 and 22 T in the
a', b and c*-directions, respectively. While the linearly increasing Hc2(T) for
H // c* indicates the multi-band effect, Hc2(0) for H // b and c* are found to
be much bigger than the BCS Pauli limiting field, 1.84 Tc ~ 9 T. The suppressed
Pauli paramagnetic effect points to a possibility of the enhanced spin-orbit
scattering related to the low dimensional electronic structure or the presence
of heavy elements such as Pd.
