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We present an analysis of our extensive data-set on IRAS 08544-4431. It isthe first object we discuss of our newly defined sample of stars, selected fortheir position in the 'RV Tauri' box in the IRAS [12]-[25], [25]-[60] two-colordiagram. Moreover, our selection criteria included an observed excess in theL-band, indicative of a dusty disc. The SED of IRAS 08544-4431 shows a broad IRexcess starting already at H. Our optical photometric data reveal some evidencefor deep and] shallow minima in the light curve and a pulsation time-scale ofaround 100 days with a small amplitude (peak-to-peak amplitude in V = 0.17mag). Our CORALIE radial velocity measurements show that IRAS 08544-4431 is abinary system with a period of 499 +/- 3 days and a mass function of 0.02M_sun. Moreover, IRAS 08544-4431 is detected in both the CO (2-1) and (1-0)mm-wave emission lines. The triangular shape of the weak CO profile confirmsthat part of the circumstellar material is not freely expanding but residesprobably in a dusty circumbinary disc. Our chemical abundance analysis of ahigh resolution spectrum of high S/N reveals that a depletion process hasmodified the photospheric abundances to a moderate extent ([Zn/Fe]=+0.4). Allthese findings confirm that the F-type IRAS 08544-4431 is another good exampleof a binary Post-AGB star surrounded by a dusty disc. The H-alpha P-Cygniprofile shows ongoing mass-loss with a very high outflow velocity, the originof which is not understood. The strength and velocity of the H-alpha-absorptionare modulated with the orbital motion; the maxima of both quantities (+/- 400km/s, 5 Angstrom, respectively) occur at superior conjunction.Comment: 14 pages, 13 figure

IRAS 08544–4431: A new post-AGB star in a binary system surrounded by a dusty disc