  Direct numerical simulations are carried out to study flow structure and
transport properties in turbulent Rayleigh-B\'{e}nard convection in a
cylindrical cell of aspect ratio one with an imposed axial magnetic field.
Flows at the Prandtl number 0.025 and the Rayleigh and Hartmann numbers up to
$10^9$ and 1400 are considered. The results are consistent with those of
earlier experimental and numerical data. As anticipated, the heat transfer rate
and kinetic energy are suppressed by strong magnetic field. At the same time,
their growth with the Rayleigh number is found to be faster in flows at high
Hartmann numbers. This behaviour is attributed to the newly discovered flow
regime characterized by prominent quasi two-dimensional structures reminiscent
of vortex sheets observed earlier in simulations of magnetohydrodynamic
turbulence. Rotating wall modes similar to those in the Rayleigh-B\'{e}nard
convection with rotation are found in flows near the Chandrasekhar linear
stability limit. Detailed analysis of the spatial structure of the flows and
its effect of global transport properties is reported.
