  Superconductivity in LaNiPO is disrupted by small (~5%) amounts of
non-stoichiometry on the lanthanum site, even though the electronic
contribution to the heat capacity increases with increasing non-stoichiometry.
All samples also exhibit specific heat anomalies consistent with the presence
of ferromagnetic spin fluctuations (Tsf ~ 14 K). Comparison of layered nickel
phosphide and nickel borocarbide superconductors reveals different
structure-property correlations in the two families.
