Context : We present the results from Suzaku observations of the hottest Abell galaxy cluster A2163 at z = 0.2 .

Aims : To study the physics of gas heating in cluster mergers , we investigated hard X-ray emission from the merging cluster A2163 , which hosts the brightest synchrotron radio halo .

Methods : We analyzed hard X-ray emission spectra accumulated from two-pointed Suzaku observations .
Non-thermal hard X-ray emission should result from the inverse Compton scattering of relativistic electrons by photons in the cosmic microwave background .
To measure this emission , the dominant thermal emission in the hard X-ray band must be modeled in detail .
To this end , we analyzed the combined broad-band X-ray data of A2163 collected by Suzaku and XMM-Newton , assuming single- and multi-temperature models for thermal emission and the power-law model for non-thermal emission .
Comparing the non-thermal hard X-ray flux to radio synchrotron emission , we also estimated the magnetic field in the cluster .

Results : From the Suzaku data , we detected significant hard X-ray emission from A2163 in the 12–60 keV band at the 28 \sigma level ( or at the 5.5 \sigma level if a systematic error of the non-X-ray background model is considered ) .
The Suzaku HXD spectrum alone is consistent with the single-temperature thermal model of gas temperature kT = 14 keV .
From the XMM-Newton data , we constructed a multi-temperature model including a very hot ( kT = 18 keV ) component in the North-East region .
Incorporating the multi-temperature and the power-law models into a two-component model with a radio-band photon index , i.e. , \Gamma = 2.18 , the 12–60 keV energy flux of non-thermal emission is constrained within 5.3 \pm 0.9 ( \pm 3.8 ) \times 10 ^ { -12 } ~ { } { erg s ^ { -1 } cm ^ { -2 } } ( the first and second errors refer to the 1 \sigma statistical and systematic uncertainties , respectively ) .
The 90 % upper limit of detected inverse Compton emission is marginal ( F _ { NT } < 1.2 \times 10 ^ { -11 } ~ { } { erg s ^ { -1 } cm ^ { -2 } } in the 12–60 keV band ) .
The estimated magnetic field in A2163 is B > 0.098 ~ { } { \mu G } .
While the present results represent a three-fold increase in the accuracy of the broad band ( 0.3–60 keV ) spectral model of A2163 , more sensitive hard X-ray observations are needed to decisively test for the presence of hard X-ray emission due to inverse Compton emission .

Conclusions :