  Several attempts have been made to detect solar-like oscillations in the G0
IV star eta Boo. We present here new observations on this star simultaneously
conducted with two spectrographs: Coralie mounted on the 1.2-m Swiss telescope
at the ESO La Silla Observatory (Chile) and Elodie based on the 1.93-m
telescope at the Observatoire de Haute Provence (France). In total, 1239
spectra were collected over 13 nights. The power spectrum of the high precision
velocity time series clearly presents several identifiable peaks between 0.4
and 1.0 mHz showing regularity with a large and small separations of Delta_nu =
39.9 uHz and delta_nu02 = 3.95 uHz respectively. Twenty-two individual
frequencies have been identified. Detailed models based on these measurements
and non-asteroseismic observables were computed using the Geneva evolution code
including shellular rotation and atomic diffusion. By combining these
seismological data with non-asteroseismic observations, we determine the
following global parameters for eta Boo: a mass of 1.57 +- 0.07 M_sol, an age
t=2.67 +- 0.10 Gyr and an initial metallicity Z/X_i=0.0391 +- 0.0070. We also
show that the mass of eta Boo is very sensitive to the choice of the observed
metallicity, while the age of eta Boo depends on the input physics used.
Indeed, a higher metallicity favours a higher mass, while non-rotating models
without overshooting predict a smaller age.
