  The atomic structure, electronic structure and physical properties of
$(TiZrNbCu)_{(1-x)}Ni_x$ (x $\leq$ 0.5) metallic glasses (MG) were studied in
both the high-entropy (0<x<0.35) and the higher Ni concentration range (x
$\geq$ 0.35). Atomic structure studies performed with X-ray diffraction and
synchrotron powder diffraction provided average atomic volumes, structure
factors, radial distribution functions, coordination numbers and packing
densities. Electronic structure studies performed using photoemission
spectroscopy and low-temperature specific heat provided information about the
electronic density of states within the valence band and at the Fermi level and
also about interatomic bonding and atomic vibrations (from the Debye
temperature and the boson peak). Variations of both atomic structure and
electronic structure with x showed a clear change for x $\geq$ 0.35, which
corresponds to a valence electron number $\geq$ 7.4. All physical properties,
namely thermal stability parameters, Debye temperatures, boson peaks, magnetic,
elastic and electronic transport properties change their
concentration-dependence for x$\geq$ 0.35. The results are compared with those
for binary and ternary MGs of the same elements.
