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We present near-infrared K-band interferometric measurements of the Mira starR Leonis obtained in April 2001 and January 2002 with the VLTI, thecommissioning instrument VINCI, and the two test siderostats. These epochscorrespond to near-maximum stellar variability phases $\sim$ 0.08 and $\sim$1.02 (one cycle later), respectively. The April 2001 data cover a range ofspatial frequencies (31--35 cycles/arcsecond) within the first lobe of thevisibility function. These measurements indicate a center-to-limb intensityvariation (CLV) that is clearly different from a uniform disk (UD) intensityprofile. We show that these measured visibility values are consistent withpredictions from recent self-excited dynamic Mira model atmospheres thatinclude molecular shells close to continuum-forming layers. We derivehigh-precision Rosseland diameters of 28.5 +/- 0.4 mas and 26.2 +/- 0.8 mas forthe April 2001 and January 2002 data, respectively. Together with literatureestimates of the distance and the bolometric flux, these values correspond tolinear radii of 350^{+50}_{-40}R$_\odot$ and 320^{+50}_{-40}R$_\odot$, and toeffective temperatures of 2930 +/- 270K and 3080 +/- 310K, respectively.Comment: 8 pages, 5 figures, accepted for publication in A&

The K-band intensity profile of R Leonis probed by VLTI/VINCI