  We present new ages and abundance measurements for the pre-main sequence star
PZ Tel. PZ Tel was recently found to host a young and low-mass companion. Using
FEROS spectra we have measured atomic abundances (e.g. Fe and Li) and
chromospheric activity for PZ Tel and used these to obtain metallicity and age
estimates for the companion. We find PZ Tel to be a rapidly rotating
(vsini=73\pm5km/s), ~solar metallicity star (logN(Fe)=-4.37 dex or [Fe/H]=0.05
dex) with a measured mean logR'HK of -4.12. We measure a NLTE lithium abundance
of logN(Li)=3.1\pm0.1dex, which from depletion models gives rise to an age of
7+4-2 Myrs for the system. The measured chromospheric activity returns an age
of 26\pm2Myrs, as does fitting pre-main sequence evolutionary tracks
(Tau_evol=22\pm3Myrs), both of which are in disagreement with the lithium age.
We speculate on reasons for this difference and introduce new models for
lithium depletion that incorporates both rotation and magnetic field affects.
We also synthesize solar, metal-poor and metal-rich substellar evolutionary
models to better determine the bulk properties of PZ Tel B, showing that PZ Tel
B is probably more massive than previous estimates, meaning the companion is
not a giant exoplanet. We show how PZ Tel B compares to other currently known
age and metallicity benchmark systems and try to empirically test the effects
of dust opacity as a function of metallicity on the near infrared colours of
brown dwarfs. Current models suggest that in the near infrared observations are
more sensitive to low-mass companions orbiting more metal-rich stars. We also
look for trends between infrared photometry and metallicity amongst a growing
population of substellar benchmark objects, and identify the need for more data
in mass-age-metallicity parameter space. [Abridged]
