  We report on the preparation of dense monofilamentary MgB2/Ni and MgB2/Fe
tapes with high critical current densities. In annealed MgB2/Ni tapes, we
obtained transport critical current densities as high as 2.3*105 A/cm2 at 4.2 K
and 1.5 T, and for MgB2/Fe tapes 104 A/cm2 at 4.2 K and 6.5 T. To the best of
our knowledge, these are the highest transport jc values at 4.2 K reported for
MgB2 based tapes so far. An extrapolation to zero field of the MgB2/Fe data
gives a critical current value of ~ 1 MA/cm2, corresponding to an critical
current value well above 1000 A. The high jc values obtained after annealing
are a consequence of sintering densification and grain reconnection. Fe does
not react with MgB2 and is thus an excellent sheath material candidate for
tapes with self-field jc values at 4.2 K in excess of 1 MA/cm2.
