  In this work we are concerned with the following class of equations
  \[
  -\Delta_p u -\lambda h(x)|u|^{p-2}u=f(x)|u|^{\gamma-2}u, \quad \mbox{in }
\mathbb{R}^N,
  \]
  involving indefinite weight functions. The existence of solution may depend
on the parameter $\lambda$. We analyze the extreme value $\lambda^{*}$ and
study its relation with the Nehari manifold. Our goal is to establish the
existence of two solutions when $\lambda>\lambda^{*}$. This work extends and
complements the results obtained by J. Chabrowski and D.G. Costa [Comm. Partial
Differential Equations 33 (2008), 1368--1394]
