ABUNDANCE ANALYSIS OF ROAP STARS .4. HD-24712

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.