In a data sample of four million hadronic Z decays collected with the
ALEPH detector at LEP, four Lambda(b) baryon candidates are exclusivel
y reconstructed in the Lambda(b) --> Lambda(c)(+) pi(-) channel, with
the Lambda(c)(+) decaying into pK(-) pi(+), <p(K)over bar (0)> or Lamb
da pi(+) pi(+) pi(-). The probability of the observed signal to be due
to a background fluctuation is estimated to be 4.2 x 10(-4). The mass
of the Lambda(b) is measured to be 5614 +/- 21 (stat.) +/- 4 (syst.)
MeV/c(2).