  Excited states in $^{212}$Po were populated by $\alpha$ transfer using the
$^{208}$Pb($^{18}$O, $^{14}$C) reaction and their deexcitation $\gamma$-rays
were studied with the Euroball array. Several levels were found to decay by a
unique E1 transition (E$_\gamma <$ 1 MeV) populating the yrast state with the
same spin value. Their lifetimes were measured by the DSAM method. The values,
found in the range [0.1-1.4] ps, lead to very enhanced transitions, B(E1) =
2$\times10^{-2}$ - 1$\times10^{-3}$ W.u.. These results are discussed in terms
of an $\alpha$-cluster structure which gives rise to states with non-natural
parity values, provided that the composite system cannot rotate collectively,
as expected in the '$\alpha$ + $^{208}$Pb' case. Such states due to the
oscillatory motion of the $\alpha$-core distance are observed for the first
time.

Nuclear Experiment;Nuclear Theory