We present the first abundance analysis of the rapidly oscillating che
mically peculiar star HD 24712, and determine a T-eff = 7250 K, log g
= 4.3, and xi(t) = 1 km s(-1). Microturbulence seems to be entirely si
mulated by a magnetic field with a polar field strength of 4.4 kG and
of dipolar structure, both of which are supported by our polarimetric
observations. Rotation of HD 24712 and a spotty surface distribution o
f the elements result in different mean abundances for different (magn
etic) phases. Our results do not support the hypothesis of a monotonic
correlation between the amplitude of abundance variations and the ato
mic number Z, and we present arguments in favour of one of the rotatio
n periods (P-rot = 12(d).4610) discussed in the literature. Rare earth
elements are the most overabundant elements relative to the sun, and
they have the largest abundance amplitude during a rotation cycle; onl
y Mg has a larger amplitude. For HD 24712 we find a clear overabundanc
e of Co while most of the other iron peak elements are underabundant.
A comparison of the abundance pattern with the other three roAp stars
analyzed so far by us concludes the paper. A systematic difference bet
ween surface gravities obtained from spectroscopy and from both astero
seismology and evolutionary tracks is found for the roAp stars HD 2471
2, alpha Cir and gamma Equ.