  The recent discovery of a zero-resistance state in nickel-based compounds has
generated a re-excitement about the long-standing problem in condensed matter
of high-critical-temperature superconductivity, in light of the analogies
between infinite-layer nickelates and cuprates. However, despite some formal
valence and crystal symmetry analogies, the electronic properties of
infinite-layer nickelates are remarkably original accounting, among other
properties, of a unique Nd5d-Ni3d hybridization. This designates infinite-layer
nickelates as a new class of oxide superconductors which should be considered
on their own. Here we report about Nd1-xSrxNiO2 (x = 0, 0.05 and 0.2) thin
films synthesized with and without a SrTiO3 capping-layer, showing very smooth
and step-terraced surface morphologies. Angle-dependent anisotropic
magnetoresistance measurements performed with a magnetic field rotating
in-plane or out-of-plane with respect to the sample surface, rendered important
information about the magnetic properties of undoped SrTiO3-capped and uncapped
samples. The results point at a key role of the capping-layer in controlling
the magnitude and the anisotropy of the anisotropic magnetoresistance
properties. We discuss this control in terms of a combined effect between the
Nd-Ni hybridization and an intra-atomic exchange coupling between the Nd-4f and
Nd-5d states, the latter essentially contributing to the (magneto)transport.
Further studies foresee the influence of the capping layer on infinite-layer
nickelates with no magnetic rare-earth.
